Showing papers by "Charles H. Peterson published in 2000"

Short-Term Consequences of Nourishment and Bulldozing on the Dominant Large Invertebrates of a Sandy Beach

Abstract: Biological responses of the dominant beach macro-invertebrates to beach nourishment and bulldozing, two widely practiced structure-free methods of responding to shoreline erosion, were evaluated along Bogue Banks, North Carolina. Sediments taken from maintenance dredging of a channel in Bogue Sound and used for beach nourishment in a replicated design were substantially finer (3.67 vs 2.33 Φ) than those of untreated beaches and contained large concentrations of shell hash. In response to nourishment, densities of Emerita talpoida and Donax spp. were lower by 86-99% on nourished beaches in early-mid July, 5-10 weeks after cessation of the nourishment project. Beach bulldozing done to augment the primary dune reduced the width of the intertidal beach by about 7 m and replaced it with a wedge of coarser, shellier sand taken from the lower beach. In late July-early August about 3 months after termination of bulldozing, counts of active burrows of ghost crabs Ocypode quadrata were 55-65% lower on bulldozed beaches, with most of the reduction occurring on the 7 m of high beach occupied by the newly formed dune face. Despite no detectable difference in slope of the lower beach, Emerita talpoida densities were 35-37% lower on bulldozed beach segments of 0.5- and 3-km, and, while Donax spp. exhibited no consistent residual response to bulldozing, two of three contrasts showed increased abundances of >100% on bulldozed segments. Failure of Emerita and Donax to recover from nourishment by mid summer when they serve as a primary prey base for important surf fishes, ghost crabs, and some shorebirds may be a consequence of the poor match in grain size and high shell content of source sediments and/or extension of the project too far into the warm season. Effects of bulldozing on ghost crabs may conceivably be mitigated by measures to stabilize the dune face after bulldozing, but the effects on Emerita and Donax are not easily interpreted so potential mitigation measures for mole crabs and bean clams are unclear.

Synthesis of linkages between benthic and fish communities as a key to protecting essential fish habitat

Abstract: Several essential fish habitats lack the protections necessary to prevent degradation because of failure to integrate the scientific disciplines required to understand the causes of the degradation and failure to integrate the fragmented state and federal management authorities that each hold only a piece of the solution. Improved protection of essential habitat for demersal fishes requires much better synthesis of benthic ecology, fisheries oceanography, and traditional fisheries biology. Three examples of degraded habitat for demersal fishes and shellfishes are high-energy intertidal beaches, subtidal oyster reefs, and estuarine soft bottoms. In each case, both scientific understanding of and management response to the problem require a holistic approach. Intertidal beach habitat for surf fishes could be protected by constraints on the character of sediments used in beach nourishment and restriction of nourishment activity to biologically inactive seasons. Subtidal oyster-reef habitat for numerous crabs, shrimps, and finfishes could be protected and restored by reduction of nitrogen loading to the estuary and elimination of dredge damage to reefs. Estuarine soft-bottom habitat for demersal fin- and shellfishes could also be protected by reduction of the nutrient loading of the estuary, which could prevent associated problems of nuisance blooms and low dissolved oxygen. Although a broad general understanding of the nature of habitat degradation exists for each of these three examples, the interdisciplinary science needed to sort out the separate and interactive contributions of all major contributing factors is incomplete. Adopting the holistic approach embodied in the principles of ecosystem management sets a course for addressing both the scientific inadequacies and the management inaction.

Tubeworm succession at hydrothermal vents: use of biogenic cues to reduce habitat selection error?

Abstract: Species colonizing new deep-sea hydrothermal vents along the East Pacific Rise show a distinct successional sequence: pioneer assemblages dominated by the vestimentiferan tubeworm Tevnia jerichonana being subsequently invaded by another vestimentiferan Riftia pachyptila, and eventually the mussel Bathymodiolus thermophilus. Using a manipulative approach modified from shallow-water ecological studies, we test three alternative hypotheses to explain the initial colonization by T. jerichonana and its subsequent replacement by R. pachyptila. We show that R. pachyptila and another vestimentiferan, Oasisia alvinae, colonized new surfaces only if the surfaces also were colonized by T. jerichonana. This pattern does not appear to be due to restricted habitat tolerances or inferior dispersal capabilities of R. pachyptila and O. alvinae, and we argue the alternative explanation that T. jerichonana facilitates the settlement of the other two species and is eventually outcompeted by R. pachyptila. Unlike the classic model of community succession, in which facilitating species promote their own demise by modifying the environment to make it more hospitable for competitors, we suggest that T. jerichonana may produce a chemical substance that induces settlement of these competitors. This process of selecting habitat based on biogenic cues may be especially adaptive and widespread among later-successional species that occupy a physically variable and unpredictable environment. In these cases, the presence of weedy species implies some integrated period of environmental suitability, whereas an instantaneous assessment of physical habitat conditions, such as water temperature for vent tubeworms, provides a poorer predictor of long-term habitat suitability.

Marine ecological research in seashore and seafloor systems: Accomplishments and future directions

Abstract: Research in seashore and seafloor communlt~es has contributed mmensely to the conceptual growth of ecology Here we summarize some of the most Important findings and discuss needs and opportunities for future work Dispropoi t~onately large numbers of the most influential contrlbutlons are derived from studies of rocky short 5 and coral reefs because aspects of these systems (accessibility) and of their most common species (sessile or weaklv motile, high density short generation tline) make them well suited to manipulative experiments Foremost among the research contributions froin seashore and seafloor systems are increased understanding of (1) competition and consumer-prey interactions, (2) trophic cascades and other Indirect specles ~nteractions (3) the evolution of defense and resistance in consumer-prey systems (4) the importance of propagule transport and recruitment vana t~on to adult populations (5) the impacts of physlcal d~sturbance and (6) the generation and maintenance of specles diversity on ecological t~ rne scales We acknowledge the importance of manipulative expenments in the growth of marine ecology but question whether a stnct adherence to this approach will best serve future needs Some of the most pressing needs for future knowledge are (1) documenting the complex influences of spatial and temporal scales on ecological processes, (2) identifying the role of large, mobile predators in manne ecosystems, (3) understanding factors hmitlng manne autotrophs, (4) integrating historical biology and neontology and (5) appreciating intersystem linkages Increased attention to conducting arrays of expenments, taking measurements and observations, and documenting change at larger scales of space and time will provlde lnsights that are unattainable by the commonly used methodological protocols Novel approaches, including (1) evaluating and managing human disturbance for the loint purpose of conservation and learning, (2) developing stronger ties between scientists worhlng in open-ocean and near-shore systems and (3) developing collaborative prolects among scientists In the academic governmental, and pnvate sectors are required to understand many of these processes

Conditional density dependence : The flow trigger to expression of density-dependent emigration in bay scallops

Abstract: Understanding how biological interactions vary under different water flow regimes is important in systems that are known to exhibit fluctuations in flow due to storms, tidal forcing, or variation in habitat structure. We performed a series of experiments to determine the migratory response of bay scallops, Argopecten irradians concentricus Say, to changes in intraspecific density under two different, tidally oscillating flow regimes in the field: 0–0.10 m s−1 and 0–0.28 m s−1. Despite the bay scallop's ability to swim actively and achieve unaided bursts of motion covering distances on the scale of 0.5 m, the expression of density-dependent emigration was dependent on the presence of higher flows. In the low-flow regime, there was negligible emigration during 24 h at any density level (12, 25, or 62 m−2); however, emigration rate increased with density (0% at 12 m−2, 60% at 25 m−2, and 71% at 62 m−2) under the higher flow regime. These results demonstrate that flow can facilitate biological interactions, creating conditional density dependence.

Short-Term Consequences of Nourishment and Bulldozing on the Dominant Large Invertebrates of a

Abstract: Biological responses of the dominant beach macro-invertebrates to beach nourishment and bulldozing, two widely practiced structure-free methods of responding to shoreline erosion, were evaluated along Bogue Banks, North Car­ olina. Sediments taken from maintenance dredging of a channel in Bogue Sound and used for beach nourishment in a replicated design were substantially finer (3.67 vs 2.33 100% on bulldozed segments. Failure of Emerita and Donax to recover from nourishment by mid summer when they serve as a primary prey base for important surf fishes, ghost crabs, and some shorebirds may be a consequence of the poor match in grain size and high shell content of source sediments and/or extension of the project too far into the warm season. Effects of bulldozing on ghost crabs may conceivably be mitigated by measures to stabilize the dune face after bulldozing, but the effects on Emerita and Donax are not easily interpreted so potential mitigation measures for mole crabs and bean clams are unclear.