More Like this

1. Regional environmental variation and local species interactions influence biogeographic structure on oyster reefs

   https://doi.org/10.1002/ecy.2921  

   Grabowski, Jonathan H. ; Gouhier, Tarik C. ; Byers, James E. ; Dodd, Luke F. ; Hughes, A. Randall ; Piehler, Michael F. ; Kimbro, David L. ( December 2019 , Ecology)

   Although species interactions are often assumed to be strongest at small spatial scales, they can interact with regional environmental factors to modify food web dynamics across biogeographic scales. The eastern oyster (Crassostrea virginica) is a widespread foundational species of both ecological and economic importance. The oyster and its associated assemblage of fish and macroinvertebrates is an ideal system to investigate how regional differences in environmental variables influence trophic interactions and food web structure. We quantified multiple environmental factors, oyster reef properties, associated species, and trophic guilds on intertidal oyster reefs within 10 estuaries along 900 km of the southeastern United States. Geographical gradients in fall water temperature and mean water depth likely influenced regional (i.e., the northern, central and southern sections of the SAB) variation in oyster reef food web structure. Variation in the biomass of mud crabs, an intermediate predator, was mostly (84.1%) explained by reefs within each site, and did not differ substantially among regions; however, regional variation in the biomass of top predators and of juvenile oysters also contributed to biogeographic variation in food web structure. In particular, region explained almost half (40.2%) of the variation in biomass of predators of blue crab, a top predator that was prevalentmore »only in the central region where water depth was greater. Field experiments revealed that oyster mortality due to predation was greatest in the central region, suggesting spatial variation in the importance of trophic cascades. However, high oyster recruitment in the middle region probably compensates for this enhanced predation, potentially explaining why relatively less variation (17.9%) in oyster cluster biomass was explained by region. Region also explained over half of the variation in biomass of mud crab predators (55.2%), with the southern region containing almost an order of magnitude more biomass than the other two regions. In this region, higher water temperatures in the fall corresponded with higher biomass of fish that consume mud crabs and of fish that consume juvenile and forage fish, whereas biomas of their prey (mud crabs and juvenile and forage fish, respectively) was generally low in the southern region. Collectively, these results show how environmental gradients interact with trophic cascades to structure food webs associated with foundation species across biogeographic regions.

   « less
2. Biological responses of the predatory blue crab and its hard clam prey to ocean acidification and low salinity

   https://doi.org/10.3354/meps14198  

   Longmire, KS ; Seitz, RD ; Seebo, MS ; Brill, RW ; Lipcius, RN ( November 2022 , Marine Ecology Progress Series)

   How ocean acidification (OA) interacts with other stressors is understudied, particularly for predators and prey. We assessed long-term exposure to decreased pH and low salinity on (1) juvenile blue crab Callinectes sapidus claw pinch force, (2) juvenile hard clam Mercenaria mercenaria survival, growth, and shell structure, and (3) blue crab and hard clam interactions in filmed mesocosm trials. In 2018 and 2019, we held crabs and clams from the Chesapeake Bay, USA, in crossed pH (low: 7.0, high: 8.0) and salinity (low: 15, high: 30) treatments for 11 and 10 wk, respectively. Afterwards, we assessed crab claw pinch force and clam survival, growth, shell structure, and ridge rugosity. Claw pinch force increased with size in both years but weakened in low pH. Clam growth was negative, indicative of shell dissolution, in low pH in both years compared to the control. Growth was also negative in the 2019 high-pH/low-salinity treatment. Clam survival in both years was lowest in the low-pH/low-salinity treatment and highest in the high-pH/high-salinity treatment. Shell damage and ridge rugosity (indicative of deterioration) were intensified under low pH and negatively correlated with clam survival. Overall, clams were more severely affected by both stressors than crabs. In the filmed predator-preymore »interactions, pH did not substantially alter crab behavior, but crabs spent more time eating and burying in high-salinity treatments and more time moving in low-salinity treatments. Given the complex effects of pH and salinity on blue crabs and hard clams, projections about climate change on predator-prey interactions will be difficult and must consider multiple stressors.« less
3. Predator signaling of multiple prey on different trophic levels structures trophic cascades

   https://doi.org/10.1002/ecy.4050  

   Belgrad, Benjamin A. ; Smee, Delbert L. ; Weissburg, Marc J. ( May 2023 , Ecology)

   The capacity of an apex predator to produce nonconsumptive effects (NCEs) in multiple prey trophic levels can create considerable complexity in nonconsumptive cascading interactions, but these effects are poorly studied. We examined such effects in a model food web where the apex predator (blue crabs) releases chemical cues in urine that affect both the intermediate consumer (mud crabs seek shelter) and the basal prey (oysters are induced to grow stronger shells). Shelter availability and predator presence were manipulated in a laboratory experiment to identify patterns in species interactions. Then, experimentally induced and uninduced oysters were planted across high‐quality and low‐quality habitats with varying levels of shelter availability and habitat heterogeneity to determine the consistency of these patterns in the field. Oyster shell thickening in response to blue crab chemical cues generally protected oysters from mud crab predation in both the laboratory and in field environments that differed in predation intensity, structural complexity, habitat heterogeneity, and predator composition. However, NCEs on the intermediate predator (greater use of refugia) opposed the NCEs on oyster prey in the interior of oyster reefs while still providing survival advantages to basal prey on reef edges and bare substrates. Thus, the combined effects of changingmore »movement patterns of intermediate predators and morphological defenses of basal prey create complex, but predictable, patterns of NCEs across landscapes and ecotones that vary in structural complexity. Generalist predators that feed on multiple trophic levels are ubiquitous, and their potential effects on NCEs propagating simultaneously to different trophic levels must be quantified to understand the role of NCEs in food webs.

   « less
4. Salt marsh shoreline geomorphology influences the success of restored oyster reefs and use by associated fauna

   https://doi.org/10.1111/rec.12992  

   Keller, Danielle A. ; Gittman, Rachel K. ; Brodeur, Michelle C. ; Kenworthy, Matthew D. ; Ridge, Justin T. ; Yeager, Lauren A. ; Rodriguez, Antonio B. ; Fodrie, F. Joel ( July 2019 , Restoration Ecology)

   Restoration is increasingly implemented as a strategy to mitigate global declines in biogenic habitats, such as salt marshes and oyster reefs. Restoration efforts could be improved if we knew how site characteristics at landscape scales affect the ecological success of these foundation species. In this study, we determined how salt marsh shoreline geomorphologies (e.g. with variable hydrodynamic energy, fetch, erosion rates, and slopes) affect the success of restored intertidal oyster reefs, as well as how fauna utilize restored reefs and forage along marsh habitats. We constructed oyster reefs along three marsh shoreline geomorphologies in May 2012: 1) “creek” (small‐fetch, gradual‐sloped shoreline), “ramp” (large‐fetch, gradual‐sloped shoreline), and “scarp” (large‐fetch, steep‐sloped shoreline). Following recruitment, oyster spat density was greatest on ramp reefs; however, 2 years later, the highest adult oyster densities were found on creek reefs. Total nekton and blue crab catch rates in trawl nets were highest in the creek, while piscivore catch rates in gill nets were highest along the scarp shoreline. We found no difference in predation on snails in the salt marsh behind constructed reef and nonconstructed reference sites, but there were more snails consumed in the creek shoreline, which corresponded with the distribution of their major predator—bluemore »crabs. We conclude that oyster reef construction was most successful for oysters in small‐fetch, gradual‐sloped, creek environments. However, nekton abundance did not always follow the same trends as oyster density, which could suggest constructed reefs may offer similar habitat‐related functions (prey availability and refuge) already present along existing salt marsh borders.

   « less
5. Ontogenetic dietary shifts in Deinonychus antirrhopus (Theropoda; Dromaeosauridae): Insights into the ecology and social behavior of raptorial dinosaurs through stable isotope analysis

   https://doi.org/https://doi.org/10.1016/j.palaeo.2020.109780  

   Frederickson, J A ; Engel, M A ; Cifelli, R L ( May 2020 , Palaeogeography palaeoclimatology palaeoecology)

   The image of the highly intelligent, pack-hunting raptor has become engrained in scientific literature and popular works alike. First proposed to explain the relatively common co-occurrence of the large-bodied iguanodontian Tenontosaurus tilletti and the wolf-sized Deinonychus antirrhopus from the Lower Cretaceous of NorthAmerica, a canid-like social hunting structure has become the standard depiction of dromaeosaurs in popular works over the last three decades. This reconstruction is, however, problematic largely due to the fact that highly coordinated hunting strategies are rarely observed in modern archosaurs. This has led to the alternative hypothesis that D. antirrhopus was more analogous to agonistic reptilian carnivores, like the Komodo dragon (Varanus komodoensis). Among the many differences between these two analogs is how social and asocial organisms rear their young, producing a diagnostic pattern based on the presence or absence of ontogenetic dietary changes. In order to test for dietary changes through growth, stable carbon and oxygen isotope (δ13C, δ18O)analysis was performed on tooth carbonate from small (<4.5 mm crown height) and large (>9 mm crown height) D. antirrhopus specimens from two microsites from the Lower Cretaceous Cloverly (Montana) and Antlers(Oklahoma) formations. Teeth from goniopholidid crocodylians and Tenontosaurus tilletti from the Cloverly Formation were also testedmore »for comparison. The results show that the Cloverly goniopholidids, like their modern counterparts, went through a distinct transition in diet as they grew. The smallest teeth were the relatively most enriched in13C (mean = −9.32‰; n= 5), the medium-sized teeth were the most-depleted in13C(mean = −10.56‰; n = 5), and the largest teeth were intermediate (mean = −10.12‰; n= 6). These factors are characteristic of the dietary shifts seen in modern asocial reptiles. D. antirrhopus showed this same pattern in tooth samples collected from both rock units, with small teeth being the more enriched in13C (mean = −8.99‰; n= 10) and the large teeth being more depleted in13C (mean = −10.38‰; n = 10). These differences suggest that juvenile and adult D. antirrhopus from both formations likely consumed different prey. Hypothetical food sources, such as T. tilletti, are close to the13C isotopic signal of adult D. antirrhopus, consistent with the hypothesized trophic relationship (predator-prey) between these two species. Juvenile D. antirrhopus had a diet more enriched in13C, likely composed of smaller-bodied, but trophically higher species. Taken together, these data add to the growing evidence that D. antirrhopus was not a complex social hunter by modern mammalian standards« less