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1. Arctic benthos in the Anthropocene: Distribution and drivers of epifauna in West Greenland

   https://doi.org/10.1016/j.scitotenv.2024.175001  

   Maier, Sandra R; Arboe, Nanette Hammeken; Christiansen, Henrik; Krawczyk, Diana W; Meire, Lorenz; Mortensen, John; Planken, Koen; Schulz, Kirstin; van_der_Kaaden, Anna-Selma; Vonnahme, Tobias Reiner; et al (November 2024, Science of The Total Environment)

   Blasco, Julian (Ed.)

   Albeit remote, Arctic benthic ecosystems are impacted by fisheries and climate change. Yet, anthropogenic impacts are poorly understood, as benthic ecosystems and their drivers have not been mapped over large areas. We disentangle spatial patterns and drivers of benthic epifauna (animals living on the seabed surface) in West Greenland, by integrating an extensive beam-trawl dataset (326 stations, 59–75°N, 30–1400 m water depth) with environmental data. We find high variability at different spatial scales: (1) Epifauna biomass decreases with increasing latitude, sea-ice cover and water depth, related to food limitation. (2) In Greenland, the Labrador Sea in the south shows higher epifauna taxon richness compared to Baffin Bay in the north. Τhe interjacent Davis Strait forms a permeable boundary for epifauna dispersal and a mixing zone for Arctic and Atlantic taxa, featuring regional biodiversity hotspots. (3) The Labrador Sea and Davis Strait provide suitable habitats for filter-feeding epifauna communities of high biomass e.g., sponges on the steep continental slope and sea cucumbers on shallow banks. In Baffin Bay, the deeper continental shelf, more gentle continental slope, lower current speed and lower phytoplankton biomass promote low-biomass epifauna communities, predominated by sea stars, anemones, or shrimp. (4) Bottom trawling reduces epifauna biomass and taxon richness throughout the study area, where sessile filter feeders are particularly vulnerable. Climate change with diminished sea ice cover in Baffin Bay may amplify food availability to epifauna, thereby increasing their biomass. While more species might expand northward due to the general permeability of Davis Strait, an extensive colonization of Baffin Bay by high-biomass filter-feeding epifauna remains unlikely, given the lack of suitable habitats. The pronounced vulnerability of diverse and biomass-rich epifauna communities to bottom trawling emphasizes the necessity for an informed and sustainable ecosystem-based management in the face of rapid climate change 

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2. Historical biogeographic range shifts and the influence of climate change on ocean quahogs

   LeClaire, A.M. (January 2022, Holocene)

   The Holocene, starting approximately 11.7 cal ka, is characterized by distinct periods of warming and cooling. Despite these known climate events, few temperature proxy data exist in the northwestern Atlantic Ocean. One potential record of past water temperatures is preserved in the marine fossil record. Shell growth of ocean quahogs (Arctica islandica), a long-lived bivalve, can provide records of past environmental conditions. Arctica islandica habitat includes the Mid-Atlantic Bight (MAB), an area rapidly warming as a consequence of climate change. The Cold Pool, a bottom-trapped water mass on the outer continental shelf within the MAB, rarely rises above 15°C. Ocean quahogs inhabiting the MAB are confined to the Cold Pool as a consequence of an upper thermal limit for the species of ~15–16°C. Recently, dead A. islandica shells were discovered outside of the species’ present-day range, suggesting that the Cold Pool once extended further inshore than now observed. Shells collected off the Delmarva Peninsula were radiocarbon-dated to identify the timing of habitation and biogeographic range shifts. Dead shell ages range from 4400 to 60 cal BP, including ages representing four major Holocene cold events. Nearly absent from this record are shells from the intermittent warm periods. Radiocarbon ages indicate that ocean quahogs, contemporaneous with the present MAB populations, were living inshore of their present-day distribution during the past 200 years. This overlap suggests the initiation of a recent biogeographic range shift that occurred as a result of a regression of the Cold Pool following the Little Ice Age. 

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3. Historical biogeographic range shifts and the influence of climate change on ocean quahogs ( Arctica islandica ) on the Mid-Atlantic Bight

   https://doi.org/10.1177/09596836221101275  

   LeClaire, Alyssa M; Powell, Eric N; Mann, Roger; Hemeon, Kathleen M; Pace, Sara M; Sower, Jill R; Redmond, Theresa E (September 2022, The Holocene)

   The Holocene, starting approximately 11.7 cal ka, is characterized by distinct periods of warming and cooling. Despite these known climate events, few temperature proxy data exist in the northwestern Atlantic Ocean. One potential record of past water temperatures is preserved in the marine fossil record. Shell growth of ocean quahogs ( Arctica islandica), a long-lived bivalve, can provide records of past environmental conditions. Arctica islandica habitat includes the Mid-Atlantic Bight (MAB), an area rapidly warming as a consequence of climate change. The Cold Pool, a bottom-trapped water mass on the outer continental shelf within the MAB, rarely rises above 15°C. Ocean quahogs inhabiting the MAB are confined to the Cold Pool as a consequence of an upper thermal limit for the species of ~15–16°C. Recently, dead A. islandica shells were discovered outside of the species’ present-day range, suggesting that the Cold Pool once extended further inshore than now observed. Shells collected off the Delmarva Peninsula were radiocarbon-dated to identify the timing of habitation and biogeographic range shifts. Dead shell ages range from 4400 to 60 cal BP, including ages representing four major Holocene cold events. Nearly absent from this record are shells from the intermittent warm periods. Radiocarbon ages indicate that ocean quahogs, contemporaneous with the present MAB populations, were living inshore of their present-day distribution during the past 200 years. This overlap suggests the initiation of a recent biogeographic range shift that occurred as a result of a regression of the Cold Pool following the Little Ice Age. 

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4. Environmental correlates of molluscan predator–prey body size in the northern Gulf of Mexico

   https://doi.org/10.1017/pab.2023.22  

   Calderaro, Luke A.; Harnik, Paul G.; Rillo, Marina C. (February 2024, Paleobiology)

   The Mississippi River watershed drains 40% of the continental United States, and the tremendous primary productivity in the adjacent north-central Gulf of Mexico has created one of the most extensive dead zones on Earth. In contrast, smaller watersheds deliver fewer nutrients to the northeastern gulf, and consequently, productivity is limited and hypoxia is uncommon. How has variation in primary productivity, oxygen availability, and sea-surface temperature affected coastal food webs? Here, we investigate environmental controls on the size of molluscan predators and prey in the northern Gulf of Mexico using Holocene death assemblages. Linear mixed models indicate that bivalve size and the frequency of drilling predation are affected by dissolved oxygen concentrations; drilling frequency declines with declining oxygen, whereas bivalve size increases. In contrast, sea-surface temperature is positively associated with the size of molluscan predators and prey. Net primary productivity contributes relatively little to predator or prey size, and predator-to-prey size ratios do not vary consistently with environmental conditions across the northern gulf. Larger bivalves in areas of oxygen limitation may be due to decreased predation pressure and, consequently, greater prey longevity. The larger size of bivalves and predatory gastropods in warmer waters may reflect enhanced growth under these conditions, provided dissolved oxygen concentrations exceed a minimum threshold. Holocene death assemblages can be used to test long-standing hypotheses regarding environmental controls on predator−prey body-size distributions through geologic time and provide baselines for assessing the ongoing effects of anthropogenic eutrophication and warming on coastal food webs. 

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5. Low drilling percentage in Norian benthic assemblages from the Southern Italian Alps and the role of specialized durophages during the Late Triassic

   https://doi.org/https://doi.org/10.1016/j.palaeo.2018.06.034  

   Tackett, LS (January 2019, Palaeogeography, palaeoclimatology, palaeoecology)

   Drillholes represent one of the clearest lines of evidence for predation of benthic invertebrates in the fossil record and are frequently used as a primary proxy for predation intensity in the fossil record. Drillholes are abundant in the late Cretaceous and Cenozoic, but their occurrence is patchy in older deposits of the Mesozoic. The inconsistent record of drillholes in pre-Cretaceous deposits of Mesozoic age are problematic for interpretations of predation-prey dynamics and adaptive radiations, and the role of taphonomy or diagenesis have not been resolved. Here we present drilling percentages for assemblages of well-preserved shelly benthic invertebrates (mainly comprised of bivalves and rare gastropods) from the upper Norian (Upper Triassic) in northern Italy in order to compare these values with reported drilling percentages from the Carnian San Cassiano Formation, a rare Triassic sedimentary unit that has yielded many drilled fossils. The Norian fossil deposits reported here are comparable to those of the San Cassiano in terms of depositional environment, preservation, and region, and can be reasonably compared to the drilling percentage of fossils from the San Cassiano. The sampled deposits are collected from marly limestone horizons in the Argillite di Riva di Solto in the Southern Italian Alps, deposited in the Lombardian Basin, and which are interbedded with shale units containing well-preserved fish and arthropod fossils, enabling a correlation between paleoecological structure of the shelly benthos and the demersal-pelagic predator diversity. Over four hundred bivalve fossils yielded a drilling percentage of 0.24% (1/406), which is typical for fossil assemblages of this age, but the single occurrence of a drillhole in this study is in marked contrast to the many drilled specimens reported from the San Cassiano Formation deposit in Italy. The drilled specimen (with complete drillhole) was an infaunal bivalve and no incomplete drillholes were observed in other specimens. Thus, drilling percentages for the Triassic are consistently low, but present, suggesting that drilling predation was an ecologically minimal influence to benthic communities and unlikely to have driven the significant ecological changes observed in benthic communities during the Late Triassic. Although drilling predation occurred during the Late Triassic, we present an updated database of specialized durophagous predators (including fishes, sharks, and reptiles) that are likely to have been more ecologically influential on benthic communities during the Norian Stage, fishes in particular. 

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