Search for: All records

Abstract AimAnthropogenic warming of marine systems has caused biological and physiological responses that are fundamentally altering ecosystem structure. Because estuaries exist at the land‐ocean interface, they are particularly vulnerable to the effects of ocean warming as they can undergo rapid biogeochemical and hydrological shifts due to climate and land‐use change. We explored how multiple components of estuarine fish diversity—turnover, richness, and abundance—have changed in the North Atlantic and Gulf of Mexico estuaries across space and time and the drivers of change. LocationNorth Atlantic and Gulf of Mexico. TaxaFish. MethodWe compiled long‐term (>30 years), continent‐wide fisheries independent trawl surveys conducted in estuaries—from the Gulf of Maine to the Gulf of Mexico (U.S. waters)—and combined these with climate and land‐use‐land‐cover data to examine trends and ecological drivers of fish richness, abundance and turnover using mixed‐effect models. ResultsSpecies richness, abundance and turnover have increased in North Atlantic and Gulf of Mexico estuaries in the last 30 years. These changes were mediated largely by sea‐surface temperature anomalies, especially in more northern estuaries where warming has been relatively pronounced. Main ConclusionThe increasing trajectory of turnover in many estuaries suggests that fish communities have changed fundamentally from the baselines. A fundamental change in community composition can lead to an irreversible trophic imbalance or alternative stable states among other outcomes. Thus, predicting how shifting community structures might influence food webs, ecosystem stability, and human resource use remain a pertinent task. 

Abstract Foundation species, such as mangroves, saltmarshes, kelps, seagrasses, and oysters, thrive within suitable environmental envelopes as narrow ribbons along the land–sea margin. Therefore, these habitat‐forming species and resident fauna are sensitive to modified environmental gradients. For oysters, many estuaries impacted by sea‐level rise, channelization, and municipal infrastructure are experiencing saltwater intrusion and water‐quality degradation that may alter reef distributions, functions, and services. To explore decadal‐scale oyster–reef community patterns across a temperate estuary in response to environmental change, we resampled reefs in the Newport River Estuary (NRE) during 2013–2015 that had previously been studied during 1955–1956. We also coalesced historical NRE reef distribution (1880s–2015), salinity (1913–2015), and water‐quality‐driven shellfish closure boundary (1970s–2015) data to document environmental trends that could influence reef ecology and service delivery. Over the last 60–120 years, the entire NRE has shifted toward higher salinities. Consequently, oyster–reef communities have become less distinct across the estuary, manifest by 20%–27% lower species turnover and decreased faunal richness among NRE reefs in the 2010s relative to the 1950s. During the 2010s, NRE oyster–reef communities tended to cluster around a euhaline, intertidal‐reef type more so than during the 1950s. This followed faunal expansions farther up estuary and biological degradation of subtidal reefs as NRE conditions became more marine and favorable for aggressive, reef‐destroying taxa. In addition to these biological shifts, the area of suitable bottom on which subtidal reefs persist (contracting due to up‐estuary intrusion of marine waters) and support human harvest (driven by water quality, eroding from up‐estuary) has decreased by >75% since the natural history of NRE reefs was first explored. This “coastal squeeze” on harvestable subtidal oysters (reduced from a 4.5‐km to a 0.75‐km envelope along the NRE's main axis) will likely have consequences regarding the economic incentives for future oyster conservation, as well as the suite of services delivered by remaining shellfish reefs (e.g., biodiversity maintenance, seafood supply). More broadly, these findings exemplify how “squeeze” may be a pervasive concern for biogenic habitats along terrestrial or marine ecotones during an era of intense global change. 

Abstract The 2010Deepwater Horizon(DwH) disaster challenged the integrity of the Gulf of Mexico (GOM) large‐marine ecosystem at unprecedented scales, prompting concerns of devastating injury for GOM fisheries in the post‐spill decade. Following the catastrophe, projected economic losses for regional commercial, recreational, and mariculture sectors for the decade after oiling were US$3.7–8.7 billion overall, owing to the vulnerability of economically prized, primarily nearshore taxa that support fishing communities. State and federal fisheries data during 2000–2017 indicated that GOM fishery sectors appeared to serve as remarkable anchors of resilience following the largest accidental marine oil spill in human history. Evidence of post‐disaster impacts on fisheries economies was negligible. Rather, GOM commercial sales during 2010–2017 were US$0.8–1.5 billion above forecasts derived using pre‐spill (2000–2009) trajectories, while pre‐ and post‐spill recreational fishery trends did not differ appreciably. No post‐spill shifts in target species or effort distribution across states were apparent to explain these findings. Unraveling the mechanisms for this unforeseen stability represents an important avenue for understanding the vulnerability or resilience of human–natural systems to future disturbances. FollowingDwH, the causes for fishery responses are likely multifaceted and complex (including exogenous economic forces that typically affect fisheries‐dependent data), but appear partially explained by the relative ecological stability of coastal fishery assemblages despite widespread oiling, which has been corroborated by multiple fishery‐independent surveys across the northern GOM. Additionally, we hypothesize that damage payments to fishermen led to acquisition or retooling of commercial fisheries infrastructure, and subsequent rises in harvest effort. Combined, these social–ecological dynamics likely aided recovery of stressed coastal GOM communities in the years afterDwH, although increased fishing pressure in the post‐spill era may have consequences for future GOM ecosystem structure, function, and resilience. 

Abstract Over heterogeneous landscapes, organisms and energy move across ecological boundaries and this can have profound effects on overall ecosystem functioning. Both abiotic and biotic factors along habitat boundaries may facilitate or impede key species interactions that drive these energy flows—especially along the land–sea interface. We synthesized the literature detailing estuarine fish diets and habitat characteristics of salt marshes from U.S. East and Gulf coasts to determine patterns and drivers of cross‐boundary trophic transfers at the land–sea interface. Notably, marsh‐platform species (i.e., killifishes, fiddler crabs) appear virtually absent in the diets of transient estuarine fishes in the Gulf of Mexico, while along the South Atlantic and Mid‐Atlantic Bights, marsh‐platform species appear regularly in the diets of many transient estuarine fishes. Tidal amplitude varied across these three biogeographic regions and likely regulates the availability of marsh‐platform species to transient estuarine fishes via both access to the marsh surface for marine predators and emergence of marsh‐resident prey into the adjacent estuary (i.e., higher tidal amplitude increases predator–prey encounter rates). Surprisingly, marsh shoot density was positively correlated with the presence of marsh‐platform species in the diet, but this pattern appears to be mediated by increased tidal amplitude, suggesting the mode and periodicity of abiotic cycles drive diet structure of transient estuarine fishes more so than local habitat structural complexity. Subsequently, these processes likely influence the degree to which “trophic relay” moves energy from the marsh toward the open estuary. Understanding the dynamics that determine energy flows, spatial subsidies, and ultimately, ecosystem‐level productivity, is essential for implementation of holistic ecosystem‐based approaches to conserve and manage complex landscape mosaics. 

Major storms can alter coastal ecosystems in several direct and indirect ways including habitat destruction, stormwater-related water quality degradation, and organism mortality. From 2010–2020, ten tropical cyclones impacted coastal North Carolina, providing an opportunity to explore ecosystem responses across multiple storms. Using monthly trawl and contemporaneous seagrass surveys conducted in Back Sound, NC, we evaluated how cyclones may affect the nursery role of shallow-water biogenic habitats by examining seagrass-associated fish responses within a temperate-subtropical estuary. We employed a general before-after-control-impact approach using trawls conducted prior (before) and subsequent (after) to storm arrival and years either without (control) or with (impact) storms. We examined whether effects were apparent over short (within ~three weeks of impact) and seasonal (May-October) timescales, as well as if the magnitude of storm-related shifts varied as a function of storm intensity. Our findings suggest that the ability of these shallow-water habitats to support juvenile fishes was not dramatically altered by hurricanes. The resilience exhibited by fishes was likely underpinned by the relative persistence of the seagrass habitat, which appeared principally undamaged by storms based upon review of available–albeit limited seagrass surveys. Increasing cyclone intensity, however, was correlated with greater declines in catch and may potentially underlie the emigration and return rate of fish after cyclones. Whether estuarine fishes will continue to be resilient to acute storm impacts despite chronic environmental degradation and predicted increases major tropical cyclone frequency and intensity remains a pressing question.