Donna Marie Bilkovic

Influence of land use on macrobenthic communities in nearshore estuarine habitats

Macrobenthic community indices were examined for their ability to characterize the influence of shoreline alteration and watershed land use in nearshore estuarine environments of the Chesapeake Bay, U.S.A. Twenty-three watersheds were surveyed in 2002 and 2003 for nearshore macrobenthic assemblages, environmental parameters (i.e., dissolved oxygen, pH, total suspended solids, salinity, and sediment composition), shoreline condition, and land use. Two indices of macrobenthic biological integrity, benthic index of biological integrity in the nearshore (B-IBIN) and abundance biomass comparison (W-value), were evaluated for associations with environmental and shoreline condition, and riparian and watershed land use. Comparisons between nearshore measures of the B-IBI with offshore values (>2 m; Chesapeake Bay benthic index of biological integrity [B-IBICB]) were conducted to assess the ability of the index to reflect land use patterns at near and far proximities to shore. Nearshore macrobenthic communities were represented by a total of 94 species (mean number of species =9.2 ± 0.4 sample−1), and were dominated by the phyla Arthropoda, Annelida, and Mollusca. Temporal variability in environmental conditions and macrobenthic abundance and biomass may be attributable to the notable increase in precipitation in 2003 that led to nutrient influxes and algal blooms. For the biotic indices applied in the nearshore, the highest scores were associated with forested watersheds (W-value, B-IBIN). Ecological thresholds were identified with nonparametric change-point analysis, which indicated a significant reduction in B-IBIN and W-value scores when the amount of developed shoreline exceeded 10% and developed watershed exceeded 12%, respectively.

Macroscale Assessment of American Shad Spawning and Nursery Habitat in the Mattaponi and Pamunkey Rivers, Virginia

Abstract Variation in habitat suitability can alter the growth and mortality of early life stages of fishes but is often difficult to measure, quantify, and apply to the entire system. We designed and tested habitat suitability index (HSI) models incorporating both proximate riverine parameters and surrounding landscape features as determinates of optimal spawning and nursery areas for American shad Alosa sapidissima. American shad eggs and larvae were collected in the Mattaponi and Pamunkey rivers, Virginia, during 1997–1999 as direct evidence of nursery habitat use and indirect evidence of spawning reaches. Hydrographic, physical habitat, shoreline, and land use features were examined for associations with the presence of eggs and larvae. Principal components analyses and logistic regressions indicated the importance of hydrographic parameters (current velocity, dissolved oxygen, and depth), physical habitat features (sediment type and woody debris), forested shoreline, and land use features to the pres...

The Effects of Derelict Blue Crab Traps on Marine Organisms in the Lower York River, Virginia

Abstract Derelict (abandoned or lost) traps targeting blue crab Callinectes sapidus have the potential to affect the blue crab fishery and other marine-oriented species. We used side-scan sonar to locate derelict traps and assess their extent and accumulation rate. Experimental traps were monitored at four locations to calculate catch rates of marine organisms and trap degradation rates. In 2006, 635–676 derelict traps were identified in a 33.5-km2 area of the lower York River in Virginias portion of the Chesapeake Bay. Trap loss rates are estimated at 30%, resulting in the potential addition of over 100,000 traps annually to the Chesapeake Bay derelict trap population in Virginia. The top four species captured in the experimental traps were blue crab, Atlantic croaker Micropogonias undulates, oyster toadfish Opsanus tau, and white perch Morone americana. Experimental derelict traps captured 50.6 blue crabs·trap−1·season−1 during April–November 2006 and 13.6 Atlantic croakers·trap−1·season−1 during May–A...

Derelict fishing gear in Chesapeake Bay, Virginia: Spatial patterns and implications for marine fauna

Derelict fishing gear is a source of mortality for target and non-target marine species. A program employing commercial watermen to remove marine debris provided a novel opportunity to collect extensive spatially-explicit information for four consecutive winters (2008-2012) on the type, distribution, and abundance of derelict fishing gear and bycatch in Virginia waters of Chesapeake Bay. The most abundant form of derelict gear recovered was blue crab pots with almost 32,000 recovered. Derelict pots were widely distributed, but with notable hotspot areas, capturing 40 species and over 31,000 marine organisms. The target species, blue crab, experienced the highest mortality from lost pots with an estimated 900,000 animals killed each year, a potential annual economic loss to the fishery of

The Role of Living Shorelines as Estuarine Habitat Conservation Strategies

300,000. Important fishery species were captured and killed in derelict pots including Atlantic croaker and black sea bass. While some causes of gear loss are unavoidable, others can be managed to minimize loss.

Use of Fully Biodegradable Panels to Reduce Derelict Pot Threats to Marine Fauna

ABSTRACT Globally, shoreline protection approaches are evolving towards the incorporation of natural and nature-based features (living shorelines henceforth) as a preferred alternative to shoreline armoring. Emerging research suggests that living shorelines may be a viable approach to conserving coastal habitats (marshes, beaches, shallows, seagrasses) along eroding shorelines. Living shorelines typically involve the use of coastal habitats, such as wetlands, that have a natural capacity to stabilize the shore, restore or conserve habitat, and maintain coastal processes. They provide stability while still being dynamic components of the ecosystem, but due to their dynamic nature, careful designs and some maintenance will be required if habitat conservation is a goal. Living shorelines may represent a singular opportunity for habitat conservation in urban and developing estuaries because of their value to society as a shoreline protection approach and resilience to sea level rise. However, enhanced public acceptance and coordination among regulatory and advisory authorities will be essential to expand their use. To fully understand their significance as habitat conservation strategies, systematic and standardized monitoring at both regional and national scales is vital to evaluate the evolution, persistence, and maximum achievable functionality (e.g., ecosystem service provision) of living shoreline habitats.

Developing and Communicating a Taxonomy of Ecological Indicators: A Case Study from the Mid-Atlantic

Fishing pots (i.e., traps) are designed to catch fish or crustaceans and are used globally. Lost pots are a concern for a variety of fisheries, and there are reports that 10-70% of deployed pots are lost annually. Derelict fishing pots can be a source of mortality for target and bycatch species for several years. Because continual removal of derelict gear can be impractical over large spatial extents, modifications are needed to disarm gear once it is lost. We tested a fully biodegradable panel with a cull or escape ring designed for placement on the sides of a crab pot that completely degrades into environmentally neutral constituents after approximately 1 year. This panel is relatively inexpensive, easy to install, and can be used in multiple fisheries. We used the blue crab (Callinectes sapidus) fishery as a test case because it is a large pot fishery and blue crab pots are similar to traps used in other pot fisheries. We had commercial fishers deploy pots with panels alongside standard pots in Chesapeake Bay (U.S.A.) to assess potential effects of our experimental pots on blue crab catch. We compared the number, biomass, and size of crabs captured between standard and experimental pots and evaluated differences in catch over a crabbing season (March-November) at five locations. There was no evidence that biodegradable panels adversely affected catch. In all locations and time periods, legal catches were comparable in abundance, biomass, and size between experimental and standard pots. Properly designed biodegradable panels appear to be a viable solution to mitigate adverse effects of derelict pots.

Assessment of Chesapeake Bay Program Selection and Use of Indicators

To ensure indicators of ecosystem health are integrated into environmental decision-making, it is imperative to provide a comprehensive framework for indicator selection and use. The same framework can also be used to evaluate the utility of any given indicator. The Atlantic Slope Consortium (ASC) has developed such a framework, based upon three primary elements: 1) The specific questions to be answered (the type of indicator), recognizing the following types of questions/indicators: Condition assessment: snapshot of the current state of the system; Stressor diagnosis: identification of causative factors of condition; Communication to the public: encouraging comprehension of condition in its most elementary or integrated form; Futures assessment: estimating the probable trajectory of condition, or assessing the vulnerability of any system to a stochastic event; Evaluation: a subset of condition indicators that evaluate the effectiveness of management actions. 2) The spatial and/or temporal scale of the issue being addressed (the spatial/temporal scale over which the indicator is valid). 3) The context of the question, using categories of surrounding land use as surrogates for social choices. A Fish Community Index (FCI) developed for the ASC will provide an example of utilizing the framework to select an indicator, as well as using the framework to judge the utility of the indicator.

Linking the Abundance of Estuarine Fish and Crustaceans in Nearshore Waters to Shoreline Hardening and Land Cover

A taxonomy of environmental indicators was developed to inform management of aquatic ecosystems, and its utility was evaluated through application within the Chesapeake Bay Program. We considered a set of 82 metrics generated by this Program, using qualitative assessment of descriptive materials. We found that 30 of these metrics conveyed sufficient information about the larger system to be considered true indicators. These 30 were classified according to the proposed taxonomy into one or more of five types: condition, evaluation, diagnostic, communication, or futures. We also evaluated the scales at which these indicators function temporally and spatially. We conclude that only a limited number of indicators are designed to be diagnostic and/or designed to forecast future conditions. The scale analyses suggest the indicator set is not focused on local scales and/or the watershed component of the Bay system. The taxonomy succeeds in framing an assessment of existing indicator sets that can productively guide future development efforts.

A Numerical Modeling Approach to Predict the Effect of a Storm Surge Barrier on Hydrodynamics and Long-Term Transport Processes in a Partially Mixed Estuary

Human alteration of land cover (e.g., urban and agricultural land use) and shoreline hardening (e.g., bulkheading and rip rap revetment) are intensifying due to increasing human populations and sea level rise. Fishes and crustaceans that are ecologically and economically valuable to coastal systems may be affected by these changes, but direct links between these stressors and faunal populations have been elusive at large spatial scales. We examined nearshore abundance patterns of 15 common taxa across gradients of urban and agricultural land cover as well as wetland and hardened shoreline in tributary subestuaries of the Chesapeake Bay and Delaware Coastal Bays. We used a comprehensive landscape-scale study design that included 587 sites in 39 subestuaries. Our analyses indicate shoreline hardening has predominantly negative effects on estuarine fauna in water directly adjacent to the hardened shoreline and at the larger system-scale as cumulative hardened shoreline increased in the subestuary. In contrast, abundances of 12 of 15 species increased with the proportion of shoreline comprised of wetlands. Abundances of several species were also significantly related to watershed cropland cover, submerged aquatic vegetation, and total nitrogen, suggesting land-use-mediated effects on prey and refuge habitat. Specifically, abundances of four bottom-oriented species were negatively related to cropland cover, which is correlated with elevated nitrogen and reduced submerged and wetland vegetation in the receiving subestuary. These empirical relationships raise important considerations for conservation and management strategies in coastal environments.