SPATIAL VARIATION IN ZOOPLANKTON SIZE AND TAXONOMIC COMMUNITY STRUCTURE ALONG A 50ºN TO 50°S TRANSECT OF THE ATLANTIC

Zooplankton play a vital role in the world's oceans in terms of transport of carbon out of the surface layer and providing food for fish. Zooplankton are patchily distributed on all scales, and this has important consequences for both sampling and understanding their role in the ocean. The distribution of zooplankton on different scales forms the focus of this study. Three Atlantic Meridional Transect (AMT) cruises were carried out and data made available from three previous cruises. Zoo plankton data were collected using a combination of vertical nets and using an optical plankton counter (OPC) sampling from the pumped seawater supply. Validation of methods showed that the OPC data could reliably be converted to carbon and numerical abundance estimates for open ocean conditions. Spectral analysis suggested that surface zooplankton heterogeneity followed a power law relationship over several scales. Over the 30 to 1000 km range this was approximately -1, and for smaller and larger scales the slope was reduced. Chlorophyll was less patchy, following temperature and salinity over the same range with a slope of -1.8. Analysis of large scale heterogeneity showed clear latitudinal trends in diversity, particularly evident in the copepod genera, with low diversity at high latitudes. The size structure appeared to be more closely related to the productivity of the area, with high zooplankton biomass associated with larger zooplankton. Regions with similar copepod communities were identified. These were found to be similar to other pelagic regions, but less closely related to watermasses or production regimes. Multiple linear regression of surface zooplankton biomass showed a strong relationship with the physics (temperature and salinity), chlorophyll and the time of day, accounting for 55% of the variability. Use of the regression equations to predict new transects gave R²=0.34. Improvement could be made by dividing the transect into smaller regions. Neural networks gave enhanced predictability (R² = 0.77 for the training set, and R²= 0.47 for the novel set) with a simpler model, although similar variables were important. This study has shown that copepods show latitudinal gradient in diversity, associated with seasonality, and form regions of similarity that do not conform to biogeochemical provinces or the watermasses. Neural networks may be used to predict zooplankton abundance from a few readily available parameters.CCMS Plymouth Marine Laborator

SeaWiFS Postlaunch Technical Report Series

This report documents the scientific activities on board the Royal Research Ship (RRS) James Clark Ross (JCR) during the fifth Atlantic Meridional Transect (AMT-5), 14 September to 17 October 1997. There are three objectives of the AMT Program. The first is to derive an improved understanding of the links between biogeochemical processes, biogenic gas exchange, air-sea interactions, and the effects on, and responses of, oceanic ecosystems to climate change. The second is to investigate the functional roles of biological particles and processes that influence ocean color in ecosystem dynamics. The Program relates directly to algorithm development and the validation of remotely-sensed observations of ocean color. Because the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) instrument achieved operational status during the cruise (on 18 September), AMT-5 was designated the SeaWiFS Atlantic Characterization Experiment (SeaACE) and was the only major research cruise involved in the validation of SeaWiFS data during the first 100 days of operations. The third objective involved the near-real time reporting of in situ light and pigment observations to the SeaWiFS Project, so the performance of the satellite sensor could be determined

Diversity and abundance of pteropods and heteropods along a latitudinal gradient across the Atlantic Ocean

AbstractShelled pteropods and heteropods are two independent groups of holoplanktonic gastropods that are potentially good indicators of the effects of ocean acidification. Although insight into their ecology and biogeography is important for predicting species-specific sensitivities to ocean change, the species abundances and biogeographical distributions of pteropods and heteropods are still poorly known. Here, we examined abundance and distribution patterns of pteropods (euthecosomes, pseudothecosomes, gymnosomes) and heteropods at 31 stations along a transect from 46°N to 46°S across the open waters of the Atlantic Ocean (Atlantic Meridional Transect cruise AMT24). We collected a total of 7312 pteropod specimens belonging to at least 31 species. Pteropod abundances were low north of 40°N with <15 individuals per 1000m3, varied between 100 and 2000ind./1000m3 between 30°N and 40°S, and reached >4000ind./1000m3 just south of 40°S. This accounted for an estimated biomass of 3.2mgm−3 south of 40°S and an average of 0.49mgm−3 along the entire transect. Species richness of pteropods was highest in the stratified (sub)tropical waters between 30°N and 30°S, with a maximum of 15 species per station. The biogeographical distribution of pteropod assemblages inferred by cluster analysis was largely congruent with the distribution of Longhurst’s biogeochemical provinces. Some pteropod species distributions were limited to particular oceanographic provinces, for example, subtropical gyres (e.g. Styliola subula) or warm equatorial waters (e.g. Creseis virgula). Other species showed much broader distributions between ∼35°N and ∼35°S (e.g. Limacina bulimoides and Heliconoides inflatus). We collected 1812 heteropod specimens belonging to 18 species. Highest heteropod abundances and species richness were found between 30°N and 20°S, with up to ∼700ind./1000m3 and a maximum of 14 species per station. Heteropods were not restricted to tropical and subtropical waters, however, as some taxa were also relatively abundant in subantarctic waters. Given the variation in distribution patterns among pteropod and heteropod species, it is likely that species will differ in their response to ocean changes

Taxonomic Distinctness of Demersal Fishes of the California Current: Moving Beyond Simple Measures of Diversity for Marine Ecosystem-Based Management

BACKGROUND: Large-scale patterns or trends in species diversity have long interested ecologists. The classic pattern is for diversity (e.g., species richness) to decrease with increasing latitude. Taxonomic distinctness is a diversity measure based on the relatedness of the species within a sample. Here we examined patterns of taxonomic distinctness in relation to latitude (ca. 32-48 degrees N) and depth (ca. 50-1220 m) for demersal fishes on the continental shelf and slope of the US Pacific coast. METHODOLOGY/PRINCIPAL FINDINGS: Both average taxonomic distinctness (AvTD) and variation in taxonomic distinctness (VarTD) changed with latitude and depth. AvTD was highest at approximately 500 m and lowest at around 200 m bottom depth. Latitudinal trends in AvTD were somewhat weaker and were depth-specific. AvTD increased with latitude on the shelf (50-150 m) but tended to decrease with latitude at deeper depths. Variation in taxonomic distinctness (VarTD) was highest around 300 m. As with AvTD, latitudinal trends in VarTD were depth-specific. On the shelf (50-150 m), VarTD increased with latitude, while in deeper areas the patterns were more complex. Closer inspection of the data showed that the number and distribution of species within the class Chondrichthyes were the primary drivers of the overall patterns seen in AvTD and VarTD, while the relatedness and distribution of species in the order Scorpaeniformes appeared to cause the relatively low observed values of AvTD at around 200 m. CONCLUSIONS/SIGNIFICANCE: These trends contrast to some extent the patterns seen in earlier studies for species richness and evenness in demersal fishes along this coast and add to our understanding of diversity of the demersal fishes of the California Current

Biogeography and genetic diversity of the atlantid heteropods.

The atlantid heteropods are regularly encountered, but rarely studied marine planktonic gastropods. Relying on a small (<14 mm), delicate aragonite shell and living in the upper ocean means that, in common with pteropods, atlantids are likely to be affected by imminent ocean changes. Variable shell morphology and widespread distributions indicate that the family is more diverse than the 23 currently known species. Uncovering this diversity is fundamental to determining the distribution of atlantids and to understanding their environmental tolerances. Here we present phylogenetic analyses of all described species of the family Atlantidae using 437 new and 52 previously published cytochrome c oxidase subunit 1 mitochondrial DNA (mtCO1) sequences. Specimens and published sequences were gathered from 32 Atlantic Ocean stations, 14 Indian Ocean stations and 21 Pacific Ocean stations between 35°N and 43°S. DNA barcoding and Automatic Barcode Gap Discovery (ABGD) proved to be valuable tools for the identification of described atlantid species, and also revealed ten additional distinct clades, suggesting that the diversity within this family has been underestimated. Only two of these clades displayed obvious morphological characteristics, demonstrating that much of the newly discovered diversity is hidden from morphology-based identification techniques. Investigation of six large atlantid collections demonstrated that 61% of previously described (morpho) species have a circumglobal distribution. Of the remaining 39%, two species were restricted to the Atlantic Ocean, five occurred in the Indian and Pacific oceans, one species was only found in the northeast Pacific Ocean, and one occurred only in the Southern Subtropical Convergence Zone. Molecular analysis showed that seven of the species with wide distributions were comprised of two or more clades that occupied distinct oceanographic regions. These distributions may suggest narrower environmental tolerances than the described morphospecies. Results provide an updated biogeography and mtCO1 reference dataset of the Atlantidae that may be used to identify atlantid species and provide a first step in understanding their evolutionary history and accurate distribution, encouraging the inclusion of this family in future plankton research

The use of taxonomic relationships among species in applied ecological research: Baseline, steps forward and future challenges

Taxonomy is more than a mere exercise of nomenclature and classification of biological diversity: it profiles the identity of species by investigating their biological and ecological traits. Taxonomy is intimately related to ecology which, in turn, cannot be a mere exercise in describing ecological patterns, but instead requires deep knowledge of species’ biological structures, roles, interactions and functions. Thus, the study of taxonomic and phylogenetic relatedness of species is of paramount importance in ecological research, enabling insights into potential evolutionary patterns and processes, allowing a more comprehensive view of biodiversity, and providing opportunities to improve the assessment and monitoring of ecological changes in time and space. The work of K. Robert (‘Bob’) Clarke forged new pathways in this direction, providing new ideas and statistical tools to include and exploit taxonomic relationships in applied marine ecological studies and beyond, also inspiring the next generation of ecologists. In this short review, we synthesise the application and development of these tools and concepts in marine biodiversity research over the last three decades and suggest future pathways in this evolving field