Benthic Data Research Articles

Density data for Lake Ontario benthic invertebrate assemblages from 1964 to 2018.

Benthic invertebrates are important trophic links in aquatic food webs and serve as useful bioindicators of environmental conditions because their responses integrate the effects of both water and sediment qualities. However, long-term data sets for benthic invertebrate assemblages across broad geographic areas are rare and, even if collected, historic data sets are often not readily accessible. This data set provides densities of benthic macroinvertebrates for all taxa collected during lake-wide surveys in Lake Ontario, a Laurentian Great Lake, from 1964 to 2018. This information resulted from surveys funded by the governments of the United States and Canada to investigate the status and changes of Lake Ontario benthic community. Of the 13 lake-wide benthic surveys conducted in Lake Ontario over the course of 54 yr, we were able to acquire taxonomic data to the species level for 11 of the surveys and data to the group level for the other two surveys. Density data are provided for taxa representing the Annelida, Arthropoda, Mollusca, Cnidaria, Nemertea, and Platyhelminthes phyla. Univariate and multivariate analyses revealed that the compositional structure of Lake Ontario invertebrate assemblages differed markedly by depth and were also significantly altered by the Dreissena spp. invasion in early 1990s. The introduction of invasive dreissenids has changed the community historically dominated by Diporeia, Oligochaeta, and Sphaeriidae, to a community dominated by quagga mussels and Oligochaeta. Considering the rarity of long-term benthic data of high taxonomic resolution in lake ecosystems, this data set could be useful to explore broader aspects of ecological theory, including effects of different environmental factors and invasive species on community organization, functional and phylogenetic diversity, and spatial scale of variation in community structure. The data set could also be useful for studies on individual species including abundance and distribution, species co-occurrence, and how the patterns of dominance and rarity change over space and time. Use of this data set for academic or educational purposes is encouraged as long as the data source is properly cited using the title of this Data Paper, the names of the authors, the year of publication, the journal name, and the article number.

Size spectra analysis of a decade of Laurentian Great Lakes data

Size spectra analysis (SSA) is used to detect changes in food webs by simplifying complex community structures through abundance-versus-biomass considerations. We applied SSA to 10 years (2006–2015) of data on Great Lakes organisms ranging in size from picoplankton to macrozooplankton. Summer pelagic size spectra slopes were near the theoretical value of −1.0, but spring slopes were steeper, reflecting seasonal differences in abundance of small and large individuals. Pelagic size spectra slopes were relatively stable over the time period we examined. Height (the predicted number of organisms at the spectra midpoint) varied among lakes and was slightly higher in summer than spring in more productive basins. Including benthic data led to shallower slopes when combined with pelagic data, suggesting benthic organisms may increase food web efficiency; height was less affected by benthic data. Benthic data are not routinely included in SSA, but our results suggest they affect slopes and therefore SSA-based predictions of fish abundance. The ability of SSA to track changes in trophic energy transfer makes it a valuable ecosystem monitoring tool.

Benthic polychaete off Tanintharyi Island, Myeik Archipelago

The survey examined shallow to deep-sea benthic data on benthic fauna from the Myanmar coastal region's northern sector. Benthic samples were collected from 17 stations (26-1500m depth) off Taninthayi Island during the Mayanmar ecosystem survey of the R/V Dr. Fridtjof Nansen Research Vessel. Polychaete (25 taxa in total) had a higher proportion than other groups of benthic fauna. The range of species diversity and evenness were insignificantly different, but species richness differed. The highest species diversity, species evenness, and richness were showed in shallow areas (26 m depth). Keywords: Diversity indices, Polychaetes, Taninthayi Island, Myeik Archipelago.

Assessing the impact of trawling on benthic megafauna: comparative study of video surveys vs. scientific trawling

Abstract Most studies about benthic community use small-scale sampling methods focused on the infauna such as grabs or box-corers. The benthic data collected by scientific trawl surveys in all European waters, in the frame of the Common Fishery Policy Data Collection Multiannual Program, can be used to study the impact of large-scale fisheries such as trawling. However, the catchability of trawls is very dependent on the nature of the seabed as well as resulting ground-gear adaptations. Due to its non-destructive nature and its ability to focus on benthic macro-epifauna, towed video sampling appears to be a good alternative to monitor the impact of trawling on benthic communities. In the present work, we studied the influence of fishery induced seabed abrasion and video characteristics on nine indices, which can be used to monitor the effect of trawling on benthic communities, was studied. Among them, three indices specific to fishery effect detection based on biological traits appeared to be the best performing benthic indices with video data: modified-Trawling Disturbance Index, partial-Trawling Disturbance Index, and modified sensitivity index. The effectiveness of these indices to monitor the effect of trawling was evaluated and compared between trawl and video sampling. This work has highlighted that video sampling could be a good alternative, or at least a complementary method, to scientific trawling to monitor the effect of trawling on benthic communities in European waters.

Regionalization of benthic hard-bottom communities across the Pourtalès Terrace, Florida

The Pourtalès Terrace is an exposed hard-bottom platform located south of the Florida Keys in 200–450 m depth with a diverse deep-sea coral ecosystem dominated by stylasterid hydrocorals, octocorals, and sponges that supports recreational and commercial fisheries. Portions of the Terrace have been designated as managed areas in the absence of detailed habitat maps, which hampers identifying ecological benefits derived from such management actions. Here we report analyses of historic Terrace physiographic and geologic data with more recent high-resolution bathymetric and benthic data to statistically derive a benthic community characterization across the Terrace. Multivariate analyses of faunal density from 42 standardized sites showed spatially distinct communities: East Terrace, West Terrace, Upper Terrace Edge, Sinkholes and Lophelia Coral Mound (the southernmost record of this habitat in the continental U.S.). These corresponded to physiographic divisions into an Upper Terrace comprised of Central and Karst-like regions, and Lower Terrace. A detailed description of these communities is provided. This study presents new insights into the Terrace benthic community spatial arrangement and is a necessary step towards facilitating benthic mapping. Our recommendations highlight the information needed for benthic habitat map creation and collecting data to determine if current conservation boundaries match management goals.

Benthic and coral reef community field data for Heron Reef, Southern Great Barrier Reef, Australia, 2002\u20132018

This paper describes benthic coral reef community composition point-based field data sets derived from georeferenced photoquadrats using machine learning. Annually over a 17 year period (2002–2018), data were collected using downward-looking photoquadrats that capture an approximately 1 m2 footprint along 100 m–1500 m transect surveys distributed along the reef slope and across the reef flat of Heron Reef (28 km2), Southern Great Barrier Reef, Australia. Benthic community composition for the photoquadrats was automatically interpreted through deep learning, following initial manual calibration of the algorithm. The resulting data sets support understanding of coral reef biology, ecology, mapping and dynamics. Similar methods to derive the benthic data have been published for seagrass habitats, however here we have adapted the methods for application to coral reef habitats, with the integration of automatic photoquadrat analysis. The approach presented is globally applicable for various submerged and benthic community ecological applications, and provides the basis for further studies at this site, regional to global comparative studies, and for the design of similar monitoring programs elsewhere.

Early trajectories of benthic coral reef communities following the 2015/16 coral bleaching event at remote Aldabra Atoll, Seychelles

Documenting post-bleaching trajectories of coral reef communities is crucial to understand their resilience to climate change. We investigated reef community changes following the 2015/16 bleaching event at Aldabra Atoll, where direct human impact is minimal. We combined benthic data collected pre- (2014) and post-bleaching (2016–2019) at 12 sites across three locations (lagoon, 2 m depth; seaward west and east, 5 and 15 m depth) with water temperature measurements. While seaward reefs experienced relative hard coral reductions of 51–62%, lagoonal coral loss was lower (− 34%), probably due to three-fold higher daily water temperature variability there. Between 2016 and 2019, hard coral cover did not change on deep reefs which remained dominated by turf algae and Halimeda, but absolute cover on shallow reefs increased annually by 1.3% (east), 2.3% (west) and 3.0% (lagoon), reaching, respectively, 54%, 68% and 93% of the pre-bleaching cover in 2019. Full recovery at the shallow seaward locations may take at least five more years, but remains uncertain for the deeper reefs. The expected increase in frequency and severity of coral bleaching events is likely to make even rapid recovery as observed in Aldabra’s lagoon too slow to prevent long-term reef degradation, even at remote sites.

Opposite response modes of NADW dynamics to obliquity forcing during the late Paleogene

Although the responses of North Atlantic Deep Water (NADW) is deeply connected to orbital rhythms, those under different tectonic and atmospheric boundary conditions remain unknown. Here, we report suborbitally resolved benthic foraminiferal stable isotope data from J-anomaly Ridge in the North Atlantic from ca. 26.4–26.0 Ma. Our results indicate that the formation of NADW during that time interval was increased during the obliquity-paced interglacial periods, similar to in the Plio-Pleistocene. During the late Oligocene, the interglacial poleward shifts of the stronger westerlies in the southern hemisphere, which occurred due to the higher thermal contrasts near the upper limit of the troposphere, reinforced the Antarctic Circumpolar Current (ACC) and, in turn, the Atlantic meridional overturning circulation (AMOC). However, such a response mode in deep ocean circulation did not occur during the middle Eocene because of different tectonic boundary conditions and the immature states of the ACC. Instead, the middle Eocene interglacial conditions weakened the formation of the proto-type NADW due to less heat loss rate in high-latitude regions of the North Atlantic during high obliquity periods. Our findings highlight the different responses of deep ocean circulation to orbital forcing and show that climate feedbacks can be largely sensitive to boundary conditions.

The BenBioDen database, a global database for meio-, macro- and megabenthic biomass and densities

Benthic fauna refers to all fauna that live in or on the seafloor, which researchers typically divide into size classes meiobenthos (32/64 µm–0.5/1 mm), macrobenthos (250 µm–1 cm), and megabenthos (>1 cm). Benthic fauna play important roles in bioturbation activity, mineralization of organic matter, and in marine food webs. Evaluating their role in these ecosystem functions requires knowledge of their global distribution and biomass. We therefore established the BenBioDen database, the largest open-access database for marine benthic biomass and density data compiled so far. In total, it includes 11,792 georeferenced benthic biomass and 51,559 benthic density records from 384 and 600 studies, respectively. We selected all references following the procedure for systematic reviews and meta-analyses, and report biomass records as grams of wet mass, dry mass, or ash-free dry mass, or carbon per m2 and as abundance records as individuals per m2. This database provides a point of reference for future studies on the distribution and biomass of benthic fauna.

Shallow-Water Coral Communities Support the Separation of Marine Ecoregions on the West-Central Florida Gulf Coast

Florida’s west coast is a 170,000 km2 bedrock shelf (WFS) comprised of north-south discontinuous carbonate outcroppings extending more than 200 km from the intertidal zone to a depth of 200 m. These outcrops support diverse benthic communities, which contribute to a multi-billion dollar recreational and commercial fishing industry, yet only about 5% of their extent has been studied in detail. Benthic communities shift over a 6.5° geographic range, but the locations of these shifts are not well-defined. Previous studies have suggested a break in biogeographic regions at Tampa Bay, south at Cape Romano, and north at Cedar Key. The goal of this study was to map and investigate the shallow WFS marine hardbottom north and south of Tampa Bay, FL to identify differences in benthic communities and identify ecoregion boundaries. Habitat mapping yielded 295.89 km² of hardbottom which differed in extent between Sarasota and Pasco counties. Benthic surveys tabulated 4,079 stony coral colonies of nine species and 1,918 soft corals. Stony corals were dominated by Siderastrea radians, Oculina robusta, Solenastrea hyades, and Cladacora arbuscula less than 10 cm in diameter. Distinct differences in these communities were evident from south to north. The main community shift indicated an ecoregion boundary at, or very near, the mouth of Tampa Bay. Another shift associated with the Bahamas Fracture Zone (BFZ) occurred at the Pinellas and Pasco county border. The outputs of this work provide the first detailed benthic habitat map of the area, a detailed survey of the composition of hardbottom benthic communities in the region, identify Tampa Bay as a coastal benthic biogeographic transition, and illustrate the influence of the BFZ on coastal communities. These findings illustrate a need for additional WFS benthic research and mapping to give a more comprehensive understanding of coral community biogeography in the context of future warming conditions and the potential tropicalization. Unifying seafloor mapping data, mapping new areas with high probability of hardbottom resources, and collecting benthic community data over broader scales will refine community biogeographic zonation. This is a necessary precursor to any long-term community monitoring to detect spatial shifts in communities and population modeling.

Suborbital Hydrological Variability Inferred From Coupled Benthic and Planktic Foraminiferal‐Based Proxies in the Southeastern Mediterranean During the Last 19 ka

AbstractWe present a high‐resolution study covering the past 19 ka from the southeastern Mediterranean Sea, based on benthic foraminiferal faunas and their stable oxygen and carbon isotopes. These data are integrated with previously published and newly acquired planktic foraminiferal data from the same sediment core in order to investigate the benthic‐planktic coupling and its response to past suborbital climate variability. On a millennial timescale, foraminiferal communities and their isotopic signatures vary following three main time periods (late glacial, sapropel S1 [~10.1–6.5 ka], and mid‐Holocene to Late Holocene). Within these intervals, we identified short‐timescale changes related to the carbon export and hydrological conditions. During the deglaciation, and except for the Younger Dryas, the coupled benthic‐planktic data indicate an overall poorly mixed water column with a low productivity. During S1 event, our data confirm the presence of a highly stratified water column, with enhanced primary productivity export to the deep sea, being associated to high Nile River activity. While the foraminiferal ecosystem is strongly driven by the combined influence of overturning circulation and the Nile River activity until the end of the African humid period, we suggest a more regional eastern Mediterranean climatic‐driven response of the foraminiferal community over the mid‐Holocene to Late Holocene. A strong multicentennial variability, probably associated to solar forcing, was found for both benthic and planktic records, and a supplementary 1,600‐year mode was found for the benthic data, suggesting a potential overturning circulation‐driven forcing for the latter.

Evaluating impacts of bottom trawling and hypoxia on benthic communities at the local, habitat, and regional scale using a modelling approach

Abstract Bottom trawling disturbance and hypoxia are affecting marine benthic habitats worldwide. We present an approach to predict their effects on benthic communities, and use the approach to estimate the state, the biomass relative to carrying capacity, of the Baltic Sea at the local, habitat, and regional scale. Responses to both pressures are expected to depend on the longevity of fauna, which is predicted from benthic data from 1558 locations. We find that communities in low-salinity regions mostly consist of short-lived species, which are, in our model, more resilient than those of the saline areas. The model predicts that in 14% of the Baltic Sea region benthic biomass is reduced by at least 50%, whereas an additional 8% of the region has reductions of 10–50%. The effects of hypoxia occur over larger spatial scales and lead to a low state of especially deep habitats. The approach is based on a simple characterization of the benthic community, which comes with high uncertainty, but allows for the identification of benthic habitats that are at greatest risk and prioritization of management actions at the regional scale. This information supports the development of sustainable approaches to manage impact of human activities on benthic ecosystems.

Trait‐based approach to monitoring marine benthic data along 500 km of coastline

AbstractAimβ diversity and its linkages with ecosystem functioning remain poorly documented. This impedes our capacity to predict biodiversity changes and how they affect ecosystem functioning at scales relevant for conservation. Here, we address the functional implications of ongoing seafloor changes by characterizing at regional scale the taxonomic and functional α and β diversities of benthic habitats currently threatened by biotic homogenization.LocationWestern Europe.MethodsCombining a trait‐based approach to benthic community monitoring data covering a 7‐year period and 500 km of coast, we explored the mechanisms governing community assembly in habitats associated with two types of foundation species, intertidal seagrass and subtidal maerl beds, compared to bare sediment at similar tidal level. We assessed their spatial and temporal variability and linked these mechanisms to their repercussions at regional scale through analyses of taxonomic and functional β diversity.ResultsFoundation species locally promote taxonomic and functional diversity. Maerl fine‐scale heterogeneity promotes niche diversity and leads to high functional redundancy for the whole subtidal compartment, providing insurance for seafloor functioning. Seagrass high diversity seems more reliant on transient species and is associated with redundancy of only a few functions. Maintaining the seascapes in which seagrass are embedded seems essential to ensure their long‐term functioning. At regional scale, the locally poorer bare sediment harbour similar functional richness as biogenic habitats because of higher within‐habitat β diversity.Main conclusionsOur study reinforces the conservation value of biogenic habitats but highlights that different mechanisms underlie their local diversity, which has implications for the vulnerabilities of their associated communities. Accounting for β diversity at regional scale also stressed a potential underrated conservation value of bare sediment for benthic ecosystem functioning. Coupling trait‐based approaches to monitoring data can help link broad‐scale β diversity to its underlying drivers, bringing local mechanistic understanding closer to the scales at which biodiversity loss and management actions occur.

Caribbean Near-Shore Coral Reef Benthic Community Response to Changes on Sedimentation Dynamics and Environmental Conditions

Coral reefs are facing unprecedented global, regional and local threats that continue to degrade near-shore habitats. Water quality degradation due to unsustainable development practices at coastal watersheds is one of the greatest stressors across multiple spatial scales. The goal of this study was to assess near-shore coral reef benthic community spatio-temporal response to sedimentation patterns, weather, and oceanographic dynamics at Bahia Tamarindo and Punta Soldado in Culebra Island, Puerto Rico. Benthic data were collected across a distance gradient from the shore through high-resolution images at marked belt transects. Environmental data were assessed and contrasted with benthic assemblages using multivariate correlations and multiple linear regression. Coral colony abundance and coral recruit assemblages showed significant variation among seasons, sites and distance zones (PERMANOVA, p<0.01). Species diversity (H’n) increased at both study sites with distance from shore and the most conspicuous coral recruit species were stress-tolerant Porites astreoides, P. porites, and Siderastrea radians. Difference in coral abundance and coral recruits per site had a strong significant negative relationship with sediment characteristics and depth (p<0.05). Near-shore coral reef benthic community structure was significantly different between sites and distance zones from shore, with depth having an important role shaping reef zonation. Changes in benthic community structure were associated with local sediment distribution patterns emerging from human alteration of coastal watersheds and natural events that cause terrigenous sediment deposition and sand resuspension across the reef. Coral cover was significantly lower at zones more exposed to recurrent sedimentation stress (p<0.01). It was also correlated with sediment texture (p=0.006) and terrigenous sediment deposition (p=0.016). Scleractinian coral cover had an inverse relationship with gorgonian and macroalgae cover. In a short-term period, a pattern of increased dominance of encrusting calcareous algae Ramicrusta textilis and invasive sponge Dictyonella funicularis were documented. Changing land use and increased frequency of extreme weather events, as a consequence of global patterns of climate change, may play an important role shaping near-shore coral reefs benthic communities and could threaten the resilience of coastal regions. Therefore, collaborative and trans-disciplinary ecosystem-based management efforts are urgently needed to effectively reduce land-based stressors and foster near-shore coral reef recovery.

Bluebills and bayou bivalves: Hurricane‐driven trophic cascades affect wintering abundance of Lesser Scaup in Louisiana

AbstractThe estuaries of coastal Louisiana overwinter a continentally significant proportion of Lesser Scaup (Aythya affinis; colloquially, “bluebills”), a migratory bird species of conservation concern since population declines began in the 1980s. Thirty‐eight years of aerial waterfowl surveys of Lake Pontchartrain—an oligohaline estuarine lagoon in southeast Louisiana—show that scaup abundance fluctuates between 0 and 1,194,907 birds, though the mechanisms driving this variation are unknown. Previous studies have shown that scaup feed primarily on mollusks, and so changes in the benthic prey community have the potential to strongly influence scaup dynamics on the Lake. Benthic communities are in turn shaped by both natural and anthropogenic disturbances (e.g., hurricanes and spillway openings), potentially creating a lagged bottom‐up trophic cascade that ultimately affects scaup abundance. Using 22 yr of paired benthic invertebrate and aerial waterfowl survey data, we found scaup populations increased with the abundance of medium‐sized Rangia clams (Rangia cuneata) and Dwarf Surf Clams (Mulinia lateralis). Those prey species declined in years when the Lake was hit by a hurricane, but medium‐sized Rangia rebounded strongly the year after, likely because storm‐surge salinity induces spawning. Using long‐term aerial survey data for scaup, we indeed found strong declines on the Lake in years when a hurricane made landfall, but scaup abundance increased the following year, presumably responding to large numbers of medium‐sized Rangia. Our three‐part analysis makes a strong case for a hurricane‐driven bottom‐up trophic cascade that affects scaup populations on Lake Pontchartrain. This study adds to a growing literature demonstrating not only that estuaries are tidally and seasonally dynamic, but that punctuated disturbance events can be important for maintaining ecosystem function.

Leveraging Automated Image Analysis Tools to Transform Our Capacity to Assess Status and Trends of Coral Reefs

Digital photography is widely used by coral reef monitoring programs to assess benthic status and trends. In addition to creating a permanent archive, photographic surveys can be rapidly conducted, which is important in environments where bottom-time is frequently limiting. However, substantial effort is required to manually analyze benthic images; which is expensive and leads to lags before data are available. Using previously analyzed imagery from NOAA’s Pacific Reef Assessment and Monitoring Program, we assessed the capacity of a trained and widely used machine-learning image analysis tool – CoralNet (coralnet.ucsd.edu) - to generate fully-automated benthic cover estimates for the main Hawaiian Islands (MHI) and American Samoa. CoralNet was able to generate estimates of site-level coral cover for both regions that were highly comparable to those generated by human analysts (Pearson’s r > 0.97, and with bias of 1% or less). CoralNet was generally effective at estimating cover of common coral genera (Pearson’s r > 0.92 and with bias of 2% or less in 6 of 7 cases), but performance was mixed for other groups including algal categories, although generally better for American Samoa than MHI. CoralNet performance was improved by simplifying the classification scheme from genus to functional group and by training within habitat types, i.e., separately for coral-rich, pavement, boulder, or ‘other’ habitats. The close match between human-generated and CoralNet-generated estimates of coral cover pooled to the scale of island and year demonstrates that CoralNet is capable of generating data suitable for assessing spatial and temporal patterns. The imagery we used was gathered from sites randomly located in <30 m hard-bottom at multiple islands and habitat-types per region, suggesting our results are likely to be widely applicable. As image acquisition is relatively straightforward, the capacity of fully-automated image analysis tools to minimize the need for resource intensive human analysts opens possibilities for enormous increases in the quantity and consistency of coral reef benthic data that could become available to researchers and managers.

Mesophotic corals on the subtropical shelves of Lord Howe Island and Balls Pyramid, south-western Pacific Ocean

Subtropical reefs are predicted to be dynamic areas of change under increased warming of global sea-surface temperature. A critical knowledge gap exists for deeper, mesophotic corals in these higher-latitude settings, where little is known about their spatial and depth distributions. At the latitudinal limits of coral-reef growth in the Pacific Ocean, abundant mesophotic corals were revealed on the shelf surrounding the subtropical, mid-ocean island of Balls Pyramid, which is a World Heritage-listed and marine park-protected area. Our study extended these findings to the nearby Lord Howe Island shelf to assess mesophotic coral cover and explore spatial patterns in mesophotic benthic communities. Underwater towed-video data collected around Lord Howe Island (24 sites) were combined with existing benthic data from the Balls Pyramid shelf. Results showed that similar habitats occur across both shelves, with communities varying among inner-, mid- and outer-shelf zones. Corals were most prevalent on the Balls Pyramid mid-shelf, with selected locations around the Lord Howe Island mid-shelf reporting similar cover (maximum site-average cover of 24%). The benthic data presented in this study provide important baseline information for monitoring coral cover and detecting potential shifts in community composition under ongoing climate change.

Cross-site comparisons of Gulf Sturgeon prey assemblages throughout the northern Gulf of Mexico reveal regional differences

Gulf Sturgeon, Acipenser oxyrinchus desotoi, is listed as threatened, with critical habitat designated throughout the northern Gulf of Mexico (GOM) to protect, in part, areas where feeding occurs. Because not all critical habitat appears to provide equivalent foraging value, reliably identifying areas of relatively high vs. low prey density coupled with appropriate sediment composition may provide important management considerations. Examination of existing benthic datasets (1980-2006) across the Gulf Sturgeon’s range revealed potential prey assemblages differed geographically, with a dominance of amphipods on the northwest coast of Florida, lower overall potential prey densities in the north-central GOM, and relatively high gastropod and bivalve densities in Louisiana. Within sites, high prey densities frequently occurred where high Gulf Sturgeon activity levels previously were identified in telemetry studies, suggesting the historical benthic data sets provide information relevant to foraging habitat. Gulf Sturgeon prey assemblages were correlated with physical parameters at 11 of 14 sites examined and physical parameters included in these correlations differed between eastern and western regions. Gulf Sturgeon prey assemblages were typically correlated with depth and % sand where sand content was high, such as the eastern portion of the sturgeon’s range, as well as parts of both Mississippi Sound and Chandeleur Sound. In contrast, depth, % TOC, and DO were associated with prey assemblages in areas with low sand content in Louisiana and Alabama. These regional results indicate that management approaches on spatial scales smaller than the northern GOM should be considered.

Substantial changes in the depth distributions of benthic invertebrates in the eastern Kattegat since the 1880s.

Bottom trawling and eutrophication are well known for their impacts on the marine benthic environment in the last decades. Evaluating the effects of these pressures is often restricted to contemporary benthic data, limiting the potential to observe change from an earlier (preimpact) state. In this study, we compared benthic species records from 1884 to 1886 by CGJ Petersen with recent data to investigate how benthic invertebrate species in the eastern Kattegat have changed since preimpact time. The study shows that species turnover between old and recent times was high, ca. 50%, and the species richness in the investigation area was either unchanged or higher in recent times, suggesting no net loss of species. Elements of metacommunity structure analysis of datasets from the 1880s, 1990s, and 2000s revealed a clear change in the depth distribution structure since the 1880s. The system changed from a Quasi‐nested/Random pattern unrelated to depth in the 1880s with many species depth ranges over a major part of the studied depth interval, to a Clementsian pattern in recent times strongly positively correlated with depth. Around 30% of the 117 species recorded both in old and in recent times, including most trawling‐sensitive species, that is large, semiemergent species, showed a decrease in maximal depth of occurrence from the deeper zone fished today to the shallower unfished zone, with on average 20 m. Concurrently, the species category remaining in the fished zone was dominated by species less sensitive to bottom trawling like infauna polychaetes and small‐sized Peracarida crustaceans, most likely with short longevity. The depth interval and magnitude of the changes in depth distribution and the changes in species composition indicate impacts from bottom trawling rather than eutrophication. Furthermore, the high similarity of results from the recent datasets 10 years apart suggests chronic impact keeping the system in an altered state.

Santonian Radiolarians and Foraminifers from Brežđe Section, Western Serbia

New data on the radiolarians and foraminifers (planktonic and benthic) from the lower part of Struganik limestones (Brežđe Section, Western Serbia) are presented. The Afens perapediensis Zone of a new detailed scale based on radiolarians for the Tethyan supra-region was traced for the first time. This allowed classification of the studied deposits to a narrow stratigraphic interval, that is, the upper Santonian. The age of the studied sediments is determined in the Santonian for planktonic foraminifera because of the joint presence of abundant Marginotruncana (extinct in the latest Santonian) and Globotruncana linneiana (d’Orbigny) (which appeared in the early Santonian). The radiolarian and planktonic and benthic foraminifera data agree with one another.