Surveying Nearshore Biodiversity
Brenda Konar1, Katrin Iken1, Gerhard Pohle2, Patricia Miloslavich3, Juan Jose Cruz‐Motta3, Lisandro Benedetti‐Cecchi4, Edward Kimani5, Ann Knowlton1, Thomas Trott6, Tohru Iseto7, Yoshihisa Shirayama7
1School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Alaska, USA
2Huntsman Marine Science Centre, St. Andrews, New Brunswick, Canada
3Departamento de Estudios Ambientales, Universidad Simon Bolivar, Caracas, Venezuela
4Department of Biology, University of Pisa, Italy
5Kenya Marine and Fisheries Research Institute, Mombasa, Kenya
6Suffolk University, Boston, Massachusetts, USA
7Seto Marine Biological Laboratory, Kyoto University, Japan
The nearshore region is defined here as the area from the high intertidal down to 20 m water depth, which is the focus of the Census of Marine Life Natural Geography in Shore Areas (NaGISA) project (www.nagisa.coml.org, Fig. 2.1 and Box 2.1). The overarching goal of NaGISA is to produce nearshore biodiversity baselines with global distribution from which new scientific questions and hypothesis testing can arise, long-term monitoring can be designed, and management plans can be implemented. One of NaGISA's goals is to create accurate biodiversity estimates by producing species lists for nearshore sites around the world. Previous overall marine biodiversity estimates, which include the nearshore, range from 178,000 to more than 10 million species (Sala & Knowlton 2006). To narrow this large range and obtain specific assessments for the nearshore, more species lists from more nearshore regions of the world are needed such as those produced during the NaGISA project. One example of the use of NaGISA baseline data is to examine latitudinal trends in biodiversity. Thus far, there have been few truly global nearshore biodiversity comparisons attempted because of the lack of comparable data (e.g. Witman et al. 2004; Kerswell 2006). NaGISA contributes to our ability to make latitudinal and other spatial comparisons by establishing a standardized sampling protocol ensuring comparability of datasets and by greatly increasing the data coverage over a large latitudinal and longitudinal range. NaGISA also has initiated a growing network of scientists that will continue to accumulate data in the years to come. This project and its goals are particularly timely because of the changes in nearshore biodiversity that are resulting from increasing anthropogenic impacts and the changing climate.
|Figure 2.1 Global map showing the NaGISA regions with associated sites that have been sampled.
Box 2.1 NaGISA GenesisNaGISA began from the coastal component of Diversitas International of the Western Pacific Asia (DIWPA). DIWPA is an international program that aims to promote and facilitate biodiversity research in the Western Pacific region. This program, supported by UNESCO, the International Union of Biological Sciences (www.iubs.org), and other international organizations, aimed to increase international biodiversity studies and thus created the International Biodiversity Observation Year (IBOY). The target of the IBOY program was a matrix of selected taxa in major coastal ecosystems including temperate, subtropical, and tropical regions. The Census of Marine Life selected this program as one of its field projects under the name NaGISA, and extended spatial and taxonomic coverage so that spatial patterns of coastal marine biodiversity in all global coastal regions could be analyzed.
NaGISA is a Japanese word that translates into the “area where the sea meets the land”. Specifically, the goal of NaGISA is to assess nearshore biodiversity in rocky macroalgal and soft-bottom seagrass areas from the high intertidal to a water depth of 20 m. Within NaGISA these nearshore habitat types were chosen for two reasons. First, these habitats are known to have high biodiversity because of the three-dimensional structure provided by the macrophytes. Even in nearshore areas where soft sediments dominate, small macrophyte oases have a higher biodiversity than the surrounding soft sediments (Dunton & Schonberg 2000). Second, these habitats are fairly globally distributed, in contrast to other habitats like nearshore coral reefs that are typically restricted to warmer waters.
One of NaGISA's largest legacies is the development of a standardized sampling protocol for nearshore rocky macroalgal and seagrass habitats (Rigby et al. 2007). This protocol ensures comparability among all NaGISA data to make an evaluation of large-scale to global nearshore biodiversity patterns possible. In addition to data comparability, a major hurdle for many nearshore biodiversity surveys is a lack of taxonomic information for many groups beyond conspicuous macrofauna and flora, especially for many smaller organisms that make up much of the existing biodiversity. NaGISA's network of scientists includes local taxonomists as well as taxonomic training to ensure accurate and reliable identifications for all major taxonomic groups. However, given the comprehensive coverage resulting from NaGISA collections, a lack of taxonomic expertise still exists for many of the smaller and less charismatic organisms and in many regions of the world.
For organizational purposes, NaGISA divided the world's shorelines into eight regions: Western Pacific, Eastern Pacific, South American Seas, Caribbean Seas, Indian Ocean, Atlantic Ocean, European Seas, and Polar Seas (Fig. 2.1). As of May 2010, the NaGISA project has sampled 253 sites, of which 179 were macroalgal sites, 71 were seagrass sites, and one each was a rhodolith site, a sandy beach, and a mudflat (Table 2.1). NaGISA also organizes the world's coastline into 20-degree bins and has data coverage (at least one sampling site per bin) in about 45% of these nearshore bins so far. Also, of the 253 sites, 64 sampled so far have been sampled more than once and many are on their way to becoming long-term monitoring sites. This initial census (2000–2010) provided a baseline dataset for long-term monitoring and the information needed to answer fundamental ecological questions about spatial patterns in nearshore biodiversity. Building on this growing baseline, NaGISA data will eventually help identify the drivers that structure these nearshore communities on local, regional to global scales. Apart from its scientific value, the strength of NaGISA is that it involves local interests and stakeholders, from local community groups to elementary, high school, and university students. This allows stakeholders to become vested in the nearshore and build an on-the-ground force that uses NaGISA data to solve local management problems. NaGISA data are part of the OBIS database (Ocean Biogeographic Information System; www.iobis.org) and are thus publicly available. As of May 2010, NaGISA contributed over 47,700 records towards OBIS distributional maps with a total of over 3,100 taxa.
2.2. The Status of Regional Nearshore Biodiversity Knowledge
The nearshore region is highly accessible and, as such, has historically received much taxonomic and ecological attention from scientists and naturalists. As with other ocean biomes, taxonomic and biodiversity knowledge differs depending on geographic region and taxonomic group. Even with this varying knowledge base, nearshore field guides and scientific publications exist for most regions of the world. It is therefore surprising that before NaGISA, very few regional estimates for nearshore biodiversity existed and information regarding biodiversity patterns on the regional scale was scarce. The following is a brief highlight that describes the status of nearshore biodiversity knowledge in each of the eight NaGISA regions (Fig. 2.1).
2.2.1. Eastern Pacific (EPAC)
NaGISA sites sampled in the Eastern Pacific region span from approximately 61° N (south–central Alaska) to 24° N (Baja Mexico). Fifty-eight sites have been established in various locations along the coasts of the United States (Alaska and California), Canada (British Columbia), and Mexico (Baja) (Table 2.1). Of these sites, 13 have been sampled more than once and are becoming established monitoring sites. Some sites in Alaska were established with the assistance of local native communities, and some sites in both Alaska and California are being maintained with the assistance of various high school and university classes.
Although much research has been done in this relatively well-known region, there are no estimates for overall nearshore biodiversity. Nonetheless, some latitudinal descriptions of this region do exist. Early work demonstrated that benthic processes, such as competition and predation, caused a north–south gradient of decreasing recruitment of intertidal sessile invertebrates from Oregon to California (Connolly & Roughgarden 1998). Along the Pacific coast of North America biogeographical and oceanographic discontinuities separate rocky intertidal communities into 13 distinct spatial groups (Blanchette et al. 2008). In general, they found strong correlations between species similarity and both geographical position and sea surface temperature. Supporting this view is the observed latitudinal gradient in the recruitment of intertidal invertebrates for this region (Connolly et al. 2001). Interestingly, in this same region, Schoch et al. ( 2006) suggested that wave run-up was the most significant physical parameter that affected community structure. NaGISA has added much knowledge to this region by starting the first extensive nearshore monitoring in Alaska and by adding to existing datasets, which will allow for a more complete longitudinal comparison along the Northwestern American coast.
2.2.2. Western Pacific (WPAC)
NaGISA sites in the Western Pacific region span from approximately 43° N (Eastern Hokkaido, Japan) to 8° S (Indonesia). Twenty-eight sites have been established in various locations in Japan, Vietnam, Philippines, Thailand, Malaysia, and Indonesia (Table 2.1). Although so far none of these sites has been sampled more than once, current WPAC efforts are trying to establish several monitoring sites.
Although much research has been done in this region, particularly in Japan, there are no nearshore biodiversity estimates. Nonetheless, some latitudinal descriptions do exist along some major ocean current regimes. Along the northern Japanese coast, the subarctic, southerly flowing Oyashio current is characterized by high biomass, large individuals, and low biodiversity. In contrast, the warm, northerly flowing Kuroshio current along the southern Japanese coast is characterized by high biodiversity but low biomass (Nishimura 1974). The high biodiversity in the Kuroshio region occurs because this current transports species living in the high diversity Coral Triangle around the Philippines, Indonesia, and Malaysia to the northern subtropical and temperate regions of the western Pacific. The high biodiversity in the south Asian coastal area has sparked much research, including important taxonomic work. NaGISA has contributed to some of these publications, such as field guides on echinoderms (Yasin et al. 2008), hermit crabs (Rahayu & Wahyudi 2008), and seagrasses (Susetiono 2007).
2.2.3. European Seas (ES)
NaGISA sites sampled within the European Seas region span from approximately 55° N (Poland) to 35° N (Crete). Sampling sites have been established in the North Sea, the Baltic Sea, the East Atlantic Ocean, the Northwest Mediterranean, the Northern and Southern Adriatic Sea, and the Aegean Sea, with collaborators from Italy, the United Kingdom, Portugal, Greece, and Poland. A total of nine sites have been sampled, four of which have been sampled more than once (Table 2.1).
Although the biodiversity of individual regions within the European Seas has been the focus of intense research (Frid et al. 2003), an exhaustive analysis of biodiversity estimates, patterns, and trends is lacking. One pattern that has been noted is the replacement of large canopy algae that dominate at higher latitudes with seagrasses that become dominant in the Mediterranean, where relict kelp populations persist only in the Strait of Messina and in the Sicily Channel (Lüning 1990). NaGISA information in the ES is allowing researchers to explore nearshore processes more thoroughly than before. For example, NaGISA data have helped to show that rare species may become more abundant when the environment is variable (Benedetti-Cecchi et al. 2008).
2.2.4. Indian Ocean (IO)
The Indian Ocean NaGISA sites range latitudinally from 28° N (Egypt) to 34° S (South Africa) and are found in Kenya, Tanzania, Mozambique, India, Egypt, and South Africa. Of the 39 sites that have been sampled, seven have been sampled more than once and are on their way to becoming monitoring sites. Two of the sites in Tanzania were established and are being monitored with the assistance of high school students, both local and from the United States.
As a result of several landmark expeditions (see, for example, Ekman 1953) and later research, taxonomic knowledge of the Indian Ocean region has been expanding. However, although biodiversity estimates do exist for certain groups in particular areas, latitudinal biodiversity descriptions for this region are lacking. The southern region of the African continent is particularly high in coastal biodiversity, with estimates of over 12,000 species from southern Mozambique in the Indian Ocean to northern Namibia in the east Atlantic, representing 6% of all coastal marine species known worldwide (Branch et al. 1994; Gibbons et al. 1999; Adnan Awad et al. 2002; Griffiths 2005). Other coastal regions of the IO are largely unknown, such as the island marine fauna in India, which have been estimated to be approximately 75% unknown (Venkataraman & Wafar 2005). In the IO region, NaGISA efforts are focusing to contribute specifically to areas of currently little existing information such as India.
2.2.5. Atlantic Ocean (AO)
The Atlantic Ocean region was sampled at 13 sites ranging from approximately 47° N (Canada) to 13° N (Senegal). These sites have been located along the coasts of Canada, the United States (Maine to Connecticut), and Senegal. Sites in Canada and the United States have largely involved elementary, high school, and university students for their sampling. Of the AO sites, five have been sampled multiple times and are considered monitoring sites (Table 2.1). In 2010, at least 12 additional sites will be established and monitored in collaboration with summer science camps from Connecticut to Maine in the Unites States.
In the AO region, it is generally recognized that biodiversity increases with decreasing latitude when comparing boreal with tropical regions (Udvardy 1969). Various environmental factors, such as local habitat heterogeneity can complicate this trend at the local scale. For example, NaGISA sampling has helped to show that Cobscook Bay at the US/Canada border, contrary to the general trend, has substantially higher macroinvertebrate species diversity than areas further south (Trott 2009). In addition, there are distinct biogeographic regions in the Northwest Atlantic, including the Polar, Acadian, Virginian, and Carolinian Provinces, with distinct regional diversity patterns (Pollock 1998).
2.2.6. South American Seas (SAS)
The South American Seas sites extend from a latitude of 2° S (Ecuador) to 42° S (Argentina) and include the countries of Argentina, Ecuador, and Brazil. A total of six sites have been sampled, with both Argentinean sites being sampled twice (Table 2.1). All sites in the SAS region were sampled with the assistance of local university students.
Although much local knowledge exists within various countries in this region, good nearshore biodiversity estimates and discussions of latitudinal trends are scarce. In Brazil, 540 taxa were described associated with seagrass beds, mostly polychaetes, fish, amphipods, decapods, mollusks, foraminiferans, macroalgae, and diatoms (Couto et al. 2003). Other areas, such as the fjords in southern Chile, have received little attention so far, and recently explorations have discovered 50 new species associated with them (Haussermann & Forsterra 2009). In Chile, several marine invertebrate taxa were found to decrease in biodiversity with increasing latitude between 18° and 40–45° S, and then increase further south, probably because of the presence of sub-Antarctic fauna (Gallardo 1987; Clarke & Crame 1997; Fernandez et al. 2000). NaGISA is contributing to the overall biodiversity effort in the SAS region by attempting to establish well-distributed NaGISA sites that will greatly enhance communication among countries so that larger-scale comparisons can be made.
2.2.7. Caribbean Sea (CS)
The Caribbean Sea sites span from approximately 10° N (Venezuela) to 30° N (Florida). Although latitudinally this is the shortest NaGISA region, it has an impressive total of 81 sites from the countries of Cuba, Trinidad and Tobago, Venezuela, Colombia, and the United States (Florida). Of the 81 sites, 22 have been sampled more than once (Table 2.1). Many of the sites in Venezuela have involved university students in their sampling, and the Florida site was initiated by a high school group, which has also gone on to help other high school groups with NaGISA sampling around the world, including Greece, Zanzibar, and Egypt.
It should be noted that for the Caribbean Seas, NaGISA is the first attempt to establish a monitoring program that does not target coral systems. This is particularly important for this region because the massive changes that have occurred in coral reefs over the past several decades (Gardner et al. 2003), including an 80% drop in live coral cover in 25 years (Wilkinson 2004), have prompted an increase in hard substrate availability, which in turn might result in a phase shift from coral-dominated communities to hard-bottom macroalgal communities.
With the exception of general field guides and some specific scientific publications, no nearshore biodiversity estimates or biodiversity trends are known to exist. However, NaGISA is contributing to this knowledge, by producing the first longitudinal comparison in the CS region, which has shown that diversity decreases from west to east (J.J. Cruz-Motta, personal communication; Fig. 2.2).
2.2.8. Polar Seas (PS)
The Polar Seas region includes both the Arctic and the Antarctic. There are 13 Arctic NaGISA sites that were sampled around 70° N, off the United States coast of Alaska. Eight of these sites have been sampled multiple times and are monitoring sites (Table 2.1). In the Antarctic, six sites have been sampled at 62° S and 78° S. Five of these sites were off of the United States McMurdo Station and one was off of the Uruguayan Artigas Research Base at the Antarctic Peninsula. Of the sites around McMurdo Station, three have been sampled more than once (Table 2.1).
Biodiversity estimates are scarce for both polar regions for most taxa (see also Chapters and ). However, for macroalgae it is estimated that there are as many as 120 macroalgal species in the Antarctic (Wiencke & Clayton 2002) and slightly more in the Arctic (Wilce 1997) but with a much higher percentage of endemic species in the Antarctic. The polar regions also have little information available regarding latitudinal trends. Typically, Arctic nearshore systems are thought to be less diverse than northern temperate systems (see, for example, Kuklinski & Barnes 2008; Wlodarska-Kowalczuk et al. 2009). In the Arctic nearshore, it seems that higher diversity is typically found at more southern locations compared with northern locations (see, for example, Kedra & Wlodarska-Kowalczuk 2008). In the Antarctic, the Peninsula, which spans approximately six degrees of latitude from 62° to 68° S, shows a latitudinal macroalgal decline (Moe & DeLaca 1976). Extending this gradient further south to the Ross Sea (77° S), the southernmost location of open water, only two species of fleshy macroalgae occur (Miller & Pearse 1991). This latitudinal decline is mainly driven by reduced light availability with increasing latitude due to strong seasonality, low solar angle, and extended periods of ice cover.
2.3. Historical Knowledge of Global Nearshore Biodiversity
2.3.1. Biodiversity Gradients
Latitudinal gradients of increasing species diversity from the poles to the tropics have often been touted as a fundamental concept in terrestrial ecology (Willig et al. 2003). Many mechanisms have been proposed to explain this latitudinal gradient, but changes in temperature have been targeted as the most plausible factor in terrestrial systems. The variation in ocean temperatures over the same distance, however, is significantly smaller and the overall importance of temperature versus other physical factors has only begun to be discussed (Blanchette et al. 2008). Other mechanisms driving latitudinal trends of rocky nearshore biodiversity are primarily large-scale oceanographic conditions and local biological interactions, which can include nutrient content and, thus, primary productivity, local assemblages of herbivores and predators, the prevalence of larval stages with differing dispersal ranges, speciation rates, and so forth (Connolly & Roughgarden 1998; Roy et al. 2000; Broitman et al. 2001; Connolly et al. 2001; Rivadeneira et al. 2002; Okuda et al. 2004; Kelly & Eernisse 2007).
Debate still surrounds the existence of nearshore latitudinal biodiversity trends, especially on the global scale. The reason for this is the lack of studies actually completed at the global scale. It is time intensive and costly to sample sites globally and literature reviews are difficult to compare owing to the various biases associated with using different sampling protocols. Even with these constraints, there are two excellent examples of global studies. In one study, field sampling found that shallow subtidal boulder communities tended to have higher species numbers at equatorial sites compared with sites closer to the poles (Fig. 2.3) (Witman et al. 2004). In contrast, a study based on a literature search of nearshore algal genera found that more biodiversity hot spots occurred in temperate regions compared with tropical or polar (Kerswell 2006). Although both studies are ground-breaking as they were the first to attempt global comparisons, it should be noted that they are limited in that one was completed on a specific habitat (subtidal rock walls in 12 biogeographic regions, totaling 49 local sites) and the other focused on one taxonomic group (macroalgae). NaGISA is assisting to broaden the knowledge of global biodiversity by increasing the number and distribution of sites, increasing the range of habitats (including intertidal and subtidal rocky shores and seagrass beds), and increasing the number of taxa examined. Based on NaGISA's main target taxa, global latitudinal comparisons will be possible for macroalgae, seagrasses, mollusks, echinoderms, polychaetes, and decapods, in addition to comparisons of overall community composition in rocky shores and seagrass systems.
|Figure 2.3 Regional species richness as a function of latitude. Reproduced with permission from Witman et al. ( 2004). Copyright 2004 National Academy of Sciences, USA.
2.3.2. Biogeographic Breaks
We cannot discuss biodiversity gradients without mentioning biogeographic breaks. Biogeographic breaks are important because biodiversity gradients do not always change continuously but sometimes are abrupt owing to these breaks. Breaks can be driven by the dynamic interaction of two or more distinct water masses. This creates active transition zones where species mingle across their respective boundaries, for example, the biogeographic provinces associated with cold- and warm-water masses. These transition zones include species pools from both systems, often resulting in a high level of biodiversity at the breaks.
Biogeographic breaks are worldwide. For example, in the east Pacific, a well-studied biogeographic break is Point Conception in California. Offshore of Point Conception, the continental shelf is broad and the south-flowing California Current is deflected offshore (Brink & Muench 1986; Browne 1994). Point Conception is a “transition zone” between the warm Californian Province and the cooler water regime of the Oregonian Province, resulting in different fish, invertebrate, and algal communities on either side of this break (Horn & Allen 1978, Murray & Littler 1981; Murray & Bray 1993). Similarly, in the eastern Atlantic along the western African coast, the coastal waters of Mauritania and Senegal and adjacent areas form a transition zone between a more temperate northern zone and a warmer tropical zone farther south. Despite variations in local conditions, biodiversity patterns of fishes, invertebrates, and particularly macroalgae reflect this change within a relatively narrow 400–500 km band (Lawson & John 1987). For Eastern South African macroalgae, a biogeographic break occurs at St. Lucia, 135 km south of the Mozambique border. Here, there is a transition from a tropical Indian Ocean flora to a temperate South African flora. As another example, a biogeographic break is found in the Gulf of Maine at Penobscot Bay, Maine, where the Maine coastal current splits to flow southwest from eastern Maine. One of the resulting branches travels east and the other continues in a southwestern direction. The communities above and below this break are statistically distinct, but not within either of the two regions (Trott 2007; see also Chapter ). The already mentioned boundary of the subtropical, warm Kuroshio current and the subpolar, cold Oyashio current forms an important biogeographic break along the eastern coast of Japan, influencing patterns of diversity and biomass. There are other biogeographic breaks around the world; these are just a few to highlight their importance to biodiversity.
Some biogeographic breaks are still under investigation and highlight the need for more biodiversity studies. For example, in the Aleutian Archipelago in Alaska, a biogeographic break may exist that drives the presence of the canopy-forming kelp from only Eualaria fistulosa to the west to primarily Nereocystis luetkeana to the east (Miller & Estes 1989). However, more oceanographic and biological data are needed to identify the exact location and drivers of this possible break (Ladd et al. 2005). NaGISA is assisting in this discussion by establishing sites along the Aleutian Archipelago.
2.3.3. Nearshore Biodiversity Hot Spots
A biodiversity hot spot is a biogeographic location that contains an unusually high number of species. Hot spots may occur along a coastline where habitats are homogeneous but for some reason a particular location has high biodiversity. A hot spot also may occur at a site where habitat type is different than the surrounding environment, as commonly seen in deeper waters at seamounts surrounded by soft sediment. There are many reasons why species diversity may be higher in certain locations and these reasons are often site specific. Reasons may include change in substrate, water mass, topography, nutrient intrusions, or geologic history.
An example of a NaGISA site that is a hot spot because of a substrate change is in the Arctic Beaufort Sea (in the PS region). Here, the typically soft-bottom seafloor contains a low-diversity fauna, with only about 30 infaunal species, mainly polychaetes and amphipods (Feder & Schamel 1976; Carey & Ruff 1977; Carey et al. 1984). In this region, local biodiversity hot spots occur where boulders provide colonizable hard substrate for macroalgae and sessile epibenthic macrofauna, which attract other organisms including more than 150 species of macroalgae, invertebrates, and fish (Dunton et al. 1982).
Hot spots also can be created by oceanographic conditions, such as in the Gulf of Maine (Buzeta et al. 2003; Trott & Larsen 2003). The NaGISA site in Cobscook Bay has the highest species richness of macroinvertebrates of any bay similar in size and habitat characteristics in the Gulf of Maine, with approximately 800 known species representing all major phyla (Trott 2004). The high biodiversity of Cobscook Bay appears to result from wave exposure and the extraordinary tides this system experiences (Campbell 2004). Additional hot spots were also identified in the Bay of Fundy where NaGISA assisted the Department of Fisheries and Oceans Canada in an effort to determine Ecologically and Biologically Significant Areas (EBSA), which resulted in the identification of five EBSA's in the Quoddy Region (Buzeta & Singh 2008).
2.4. Closing Information Gaps
The field of taxonomy, traditionally based primarily on morphology, has expanded in recent years to include molecular information (Blaxter 2003; Hebert et al. 2003). This has not only enhanced our understanding of evolutionary relationships but also our knowledge of biodiversity and species distributions ranging from algae to fishes (Saunders 2005, 2008; Blum et al. 2008; Pfeiler et al. 2008; Thacker 2009). Nonetheless, our ability to identify organisms in some areas and for some taxa is still limited, leaving gaps in taxonomic knowledge as well as for particular regions of the world's coasts (see Box 2.2). Many developing countries and remote regions lack financial support, technology, and taxonomic information for their fauna and flora. This is particularly true for smaller, less charismatic organisms of no economic importance. Access to these remote regions is difficult due to logistical and financial constraints, leaving gaps in data coverage. Each of the eight NaGISA regions contains areas that have not been sufficiently explored (Fig. 2.4). The western coast of Alaska in the Eastern Pacific region, the western African coast in the Atlantic region, all of the Arctic coastline except where research stations allow access, the eastern Antarctic coast, and remote islands in the Indian Ocean are just a few examples.
|Figure 2.4 Global map showing current major biodiversity gaps (defined as missing information for most taxonomic groups) in NaGISA-focused habitats. These gaps are based on estimates by NaGISA researchers.
Box 2.2 NaGISA Contributions to the Effort of Closing Taxonomic Gaps
NaGISA conducts workshops to train new taxonomists.
NaGISA creates public ownership for coastal marine diversity.
2.5. NaGISA's Major Findings
Although the nearshore region is probably among the most-studied parts of the ocean because of its accessibility and obvious interest to humans as a resource, the lack of information on biodiversity and its large-scale and long-term patterns in more than a handful of locations is particularly surprising. Also surprising is the lack of integrated information so that regional and global trends and patterns can be discussed. NaGISA is the first project to undertake the ambitious step to create such large-scale baselines with the establishment of standardized protocols and a growing global network of nearshore researchers. With over 250 sites located around the world, and still growing, and 28 different countries involved, NaGISA is the largest-ever attempt to address truly global-scale biodiversity issues.
The central idea of the NaGISA standardized sampling protocol is a fully nested design. Replicate samples along various tidal heights are collected at each site, and multiple sites are sampled within regions of specific latitude and longitude. This hierarchical design of the protocol with replicate samples within a site, which is then nested within latitude or longitude, allows a statistically appropriate and powerful method to analyze biodiversity patterns across several spatial and temporal scales (Benedetti-Cecchi 2007). Not only can biodiversity patterns be analyzed on local, regional, and up to global scales, but it can also be determined at which of these scales most variability occurs.
NaGISA's protocols include various independent sampling levels, from cover estimates to actual collections and detailed taxonomic identification of all organisms. This design allows flexibility in sampling effort, so where the full sampling effort is not possible due to logistical or financial constraints, parts of the protocols can be used to create important local information that can be compared with large-scale NaGISA data. For example, cover estimates can be done relatively quickly, and students, agencies, or local people can be trained to do so with high scientific accuracy. This opens opportunities to perform long-term monitoring at specific sites and/or the expansion of quantitative nearshore coverage with the inclusion of added manpower from local stakeholders. NaGISA's regionally organized network of nearshore researchers allows local scientists across the world to participate in this effort and thus make the final product larger than the sum of its individual parts.
NaGISA's specific scientific findings from its field surveys include inventories of marine flora and fauna, data on their abundance and biomass, new species records, species range extensions, habitat range extensions, biodiversity hot spots, and explanations of nearshore ecological processes and biodiversity drivers. All findings can now be analyzed on regional as well as global scales.
Several new species were found and subsequently described during the NaGISA inventories. These new species discoveries included some small and inconspicuous species, like two cumaceans from the Gulf of Alaska (Cumella oculatus and C. alaskensis; Gerken 2009). These cumaceans are not only new species but their discovery was surprising as the genus Cumella is typically tropical rather than boreal–Arctic. Cumaceans, as filter feeders and surface deposit feeders, are ecologically important in energy transfer within the benthic food web and on the Alaskan shelf as they are important food for grey whales. Other, more conspicuous new species discovered were the golden V kelp in the Aleutian Islands, Alaska (Aureophycus aleuticus; Kawai et al. 2008). This kelp grows up to 3 m in length, and histological and genetic analyses show that it may not be closely related to other kelp species in the region. This opens interesting evolutionary and distributional questions about kelps in the North Pacific, where they form important habitats for associated biodiversity.
Another significant NaGISA accomplishment has been the discovery of the anomalodesmatan bivalve Pholadomya candida living in a Thalassia testudinum seagrass bed at Santa Marta, Colombia. This bivalve species belongs to the ancient family Pholadomyidae, a group of burrowing bivalves living on Earth since at least the Early Carboniferous (330 million years bp), which reached a high degree of diversification in Jurassic to Cretaceous times. Pholadomya candida had been collected alive only twice, with the last record in 1842, and, because living specimens had not been recorded for nearly 140 years, some authors considered the species extinct. The evolutionary implications of this re-discovery are remarkable. Comparative molecular sequencing of P. candida with other anomalodesmatan species and with representatives of other presumably related groups may provide clues of the evolution of the Anomalodesmata, as well as indications on the origin of the Myoida (Díaz et al. 2009).
Several new species distributional records and range extensions have been found during NaGISA sampling efforts. In the western Pacific, the solitary entoproct Loxosomella sp. was found in a seagrass sample from Akajima, Okinawa Prefecture, Japan. This is the first record of this animal group from sandy seagrass habitats in this region. Another interesting discovery was made in the Eastern Pacific with the coralline alga Phymatolithon calcareum. During NaGISA sampling, this species was found in its gametangial reproductive state (Konar et al. 2006). Although this species is relatively common and globally distributed, it was previously found only once in this reproductive state and that record was off the Atlantic coast of France (Mendoza & Cabioc'h 1998). In the well-studied Cobscook Bay of the Gulf of Maine in the Atlantic Ocean region, NaGISA surveys found tens of benthic faunal taxa previously unreported from the area, from such diverse groups as hydrozoans (for example Clytia gracilis), mollusks (for example Spisula solidissima, Astarte portlandica), crustaceans (for example Nebalia bipes, Metopella carinata), polychaete worms (for example Aricidea albatrossae, Euchone papillosa), and bryozoans (for example Haplota clavata, Cribrilina punctata). Similarly, new species records for five macroalgal species were found at NaGISA sites in the Arctic Beaufort Sea, including the brown algae Sphacelaria plumosa and S. arctica, and the red algae Rhodomela tenuissima and Scagelia cf americana. Also at these sites, the common red alga Phyllophora truncata was often infested with what has been tentatively identified as an endophytic alga Chlorochytrium.
In addition to species-level discoveries, NaGISA also had some significant discoveries of habitat extensions. A major range extension was the discovery of a rhodolith habitat in the Eastern Pacific region (Konar et al. 2006). Rhodoliths are unattached calcareous red algae that form extensive beds, which provide habitat for many associated, sometimes commercially important species. Although rhodolith beds are widely distributed in temperate and tropical areas, the rhodolith bed discovery in Alaska's Prince William Sound in the North Pacific Ocean represents a significant northward extension of known rhodolith distribution. Also, in the Arctic Beaufort Sea, a new boulder field providing substrate for a diverse community of macroalgae and invertebrates was mapped in Camden Bay through NaGISA efforts (Iken & Konar 2007).
Regional comparisons have already yielded new insights into biodiversity patterns. Longitudinal comparisons in the Caribbean Seas region have shown that there is a decrease in species numbers from west to east. At the same time, this gradient in species numbers is not similarly reflected in the taxonomic structure of the communities (based on the index of taxonomic distinctiveness) as this is the same along that longitudinal gradient (Fig. 2.2). The nested design of the NaGISA sampling protocol was used in the Gulf of Alaska in the EPAC region to analyze the contributions of local versus regional scales of variability in nearshore communities (Konar et al. 2009). Interestingly, most variability was associated with the local scale and very little with regional scales. On the local scale, the depth gradient was the most important factor contributing to variability, which was also found when only echinoderm distribution was analyzed over the same spatial scales (Chenelot et al. 2007). The number of species generally increases from the high intertidal to a depth of 1 m and then decreases with increasing subtidal depths. The large tidal range in the region effectively renders the 1 m depth stratum low intertidal and thus a suitable interface for a large variety of intertidal and subtidal organisms (Konar et al. 2009). Seasonal comparisons in the South American region (Puerto Madryn, Argentina) found that local biodiversity varies throughout an annual cycle in close relation to the presence of an invasive brown algal species (Undaria pinnatifida), which is sensitive to warm temperatures. During the austral winter, U. pinnatifida invades the rocky substrates replacing the natural community, but also attracts another community of gastropods, polychaetes, sea urchins, and other invertebrates that feed on the algae. As the water temperature increases in the austral summer, U. pinnatifida dies, and the natural community returns.
Along with reporting community patterns and biodiversity trends, it also is important to explain why and how these trends and patterns exist. Some research has already examined drivers of community patterns and biodiversity trends at various spatial scales (Coleman et al. 2006; Kuklinski et al. 2006; Scrosati & Heaven 2007; Wulff et al. 2009). NaGISA in the European Seas conducted an experimental study using a combination of long-term observations and field manipulations to show that rare species take advantage of environmental variability, becoming less rare in fluctuating environments (Benedetti-Cecchi et al. 2008). Hence, an increase in environmental variability, such as that expected under climate change models, may lead to major shifts in species composition within assemblages, with the prediction that currently rare species may become more dominant with increasing levels of environmental heterogeneity.
2.6. Remaining Questions
Although NaGISA efforts are greatly contributing to the field of nearshore biodiversity, many issues and questions remain. First and foremost, true estimates for global nearshore biodiversity do not exist. The million dollar question of how many organisms live in nearshore waters, still cannot be answered. It appears that the more regions that are sampled and the more taxonomists that are involved, the more new species and range extensions are found. We may never know exactly how many species live in the nearshore, but we can and should continue working towards increasingly accurate estimates.
Another question that still remains open is why certain areas have higher biodiversity (or abundances or biomass) than other areas. The more we learn about biodiversity trends and the physical and biological attributes that contribute to biodiversity hot spots, the easier it will be to answer the question of why these hot spots exist. From the data currently available, it appears that many of the hot spots occur because of various site-specific parameters (that is, hard substrate in an otherwise soft substrate environment, local oceanographic conditions). However, more information is needed to determine if and what biological and physical parameters will result in the existence of a hot spot and if large-scale generalizations of such relationships can be made.
Along with the questions, some problems also remain. One such problem that still exists in many regions is the surveying of remote and isolated areas. With the advances in remote sensing, these areas are becoming more accessible. The intertidal zone can be surveyed with remote sensing, using Ikonos satellite imaging (www.satimagingcorp.com/gallery-ikonos.html), followed by hyperspectral imaging and ground-truthing (Larsen et al. 2009). In some areas, like the northern part of the Eastern Pacific region, programs exist that have already mapped nearshore coasts, such as the ShoreZone project (alaskafisheries.noaa.gov/habitat/shorezone/szintro.htm), and these images are available online. In many areas, the subtidal areas can be mapped and information such as bottom type and depth can be acquired from multibeam sonar acoustic mapping. This can then be ground-truthed with benthic sampling. This type of information will make discovering new biodiversity hot spots and describing patterns and processes in the nearshore much easier. Nevertheless, although such mapping efforts can supply guidance and large-scale coverage, the need for local ground-truthing and traditional establishment of biodiversity remains.
Although there has been much advancement in the knowledge of nearshore biodiversity, education in developing countries must continue. It has become evident that there is a need for expert services and facilities to process field samples efficiently and completely. Some regions have this service, such as the Atlantic Ocean region through the Atlantic Reference Centre (Huntsman Marine Science Centre, New Brunswick, Canada), which is in charge of processing, quality control/assurance, and archiving all Atlantic Ocean regional samples.
Current NaGISA data will culminate in 2010 with assessing spatial (for example latitudinal or longitudinal) trends of overall community patterns in rocky macroalgal systems and seagrass beds, as well as of selected taxonomic groups. Because of the relatively good taxonomic expertise available in most regions of the world, NaGISA is focusing in this first phase on patterns in macroalgae, polychaetes, gastropods, echinoderms, and decapods. However, there are many other taxonomic groups that are yet unexplored, but are no less ecologically important. Not only do we know that biodiversity trends vary depending on the taxonomic group examined, but these patterns may be quite different for the rarer groups than the more common taxa. Similarly we have learned that biodiversity trends often depend on the depth strata examined, but without better knowledge of small-scale biodiversity patterns, overall trends will be difficult to determine. There are many questions that remain unanswered here, such as what is the global latitudinal trend for cnidarians, sponges, or bryozoans, and do these trends vary with depth.
NaGISA's major legacies thus far can be summarized as the following.
The creation of the first standardized global baseline of coastal biodiversity in rocky shores and seagrass beds from the intertidal zone to water depths of up to 20 m.
The establishment of a standardized sampling protocol that is suitable to analyze biodiversity trends on multiple spatial and temporal scales.
The improvement of benthic taxonomy.
The network of scientists and new scientific capacity-building around the world, a network that is now working together to address major questions in nearshore biodiversity.
The elucidation of the scales of temporal and spatial variability in nearshore habitats.
The addition of knowledge on the interactive effects of multiple drivers, including human activities, on spatial patterns of marine coastal biodiversity at the global scale.
The identification of hot spots of marine coastal biodiversity that can be suggested for new Marine Protected Areas.
The NaGISA project has sampled many sites throughout the world, but the efforts are still dwarfed compared with the vastness of the world's nearshore region. Some of the sampled sites have now been established for long-term monitoring. In all regions, there will and should be continued monitoring of selected NaGISA sites. This monitoring will be done by a combination of researchers, elementary, high school, and university students, local communities, and other stakeholders. NaGISA has particularly enhanced stakeholder “ownership” at many sites, similar to sponsorship of roadside clean-up programs. Although information for truly global comparisons is still lacking in many areas and for certain taxonomic groups, patterns in biodiversity are beginning to emerge. More sites are continually being added and more taxonomists are being engaged. The momentum that NaGISA has started must continue if we are to get an increasingly accurate description of global diversity.
The NaGISA monitoring sites will assist with the identification of inter-annual variability. This is crucial to be able to distinguish short-term variability from longer-term changes that may be driven by climatic changes or anthropogenic pressures. Such long-term changes will become measurable over time from NaGISA sites that are part of the long-term monitoring. In addition, the NaGISA–History of Marine Animal Populations collaboration, the History of the Nearshore (HNS) project, is identifying changes in nearshore communities that have occurred over decadal scales. By comparing historical baselines with present-day data, regional changes within the various HNS studies may be detected. Changes revealed by comparisons of several Atlantic HNS regions could, for example, produce a Pan-Atlantic pattern and identify driving factors.
NaGISA has done much to not only advance the knowledge and appreciation of nearshore biodiversity, but it has started a momentum through its outreach, networking, and capacity building. We may never be able to answer how many species live in the nearshore, but we will continue to produce a more accurate estimation and to explain why there are so many nearshore species and why they are distributed as they are.
We thank the many unnamed scientists, students, and interested people who have helped to sample the nearshore environment all over the world to contribute to the NaGISA effort. Specifically for the EPAC region, we thank Rafael Riosmena-Rodriguez (Universidad Autónoma de Baja California Sur) and Matthew Edwards (San Diego State University) for data and input into various sections of this chapter. In the SAS region, Gabriela Palomo (Museo Argentino de Ciencias Naturales MACN, Argentina), Manuel Ortiz (Universidad de La Habana, Cuba), Gregorio Bigatti (Centro Nacional Patagonico CENPAT, Argentina), Manuel Cruz (INOCAR and Facultad Ciencias Naturales, Universidad de Guayaquil, Ecuador), and Paulo Lana (Universidade Federal do Paraná, Brazil) provided data summarized in Table 2.1. In the Caribbean Sea region, the following individuals provided information and feedback: Diana Isabel Gómez (INVEMAR, Colombia), Judith Gobin (University of West Indies, Trinidad and Tobago), Manuel Ortiz (Universidad de La Habana, Cuba), and Andrea Bueno (Universidad Simon Bolivar, Venezuela). Lastly, we remember P. Robin Rigby (1977–2007) whose leadership has been essential in creating the NaGISA network.
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