Drew Carey

Towards a greater understanding of pattern, scale and process in marine benthic systems: a picture is worth a thousand worms

Historically, advances in our knowledge of benthic community structure and functioning have necessarily relied upon destructive sampling devices (grabs, cores, anchor dredges, etc.) that lose valuable contextual information in the process of sampling. In the last 40 years, instrumentation capable of measuring dynamic events and/or processes within and immediately above the seafloor has been developed that facilitates the collection of ecological information. Of these, both acoustic and optical imaging devices have played a significant role in revealing much about the physiology and behaviour of, and interactions between benthic species, and the sedimentary habitat in which they reside. While a number of reviews have separately considered the methodological and technical aspects of imaging technologies, the collective contribution that imaging has made to benthic ecology has received less attention. In this short review, we attempt to highlight key instances over the last 40 years where either acoustic or optical-based imaging techniques have provided new ecological insights and information about fine-grained sedimentary environments. In so doing, we focus on the ecological advances that have formed the precursor to current research efforts and introduce some of the latest revelations from appropriate and emerging imaging applications.

Use of laser line scan for assessment of response of benthic habitats and demersal fish to seafloor disturbance

Abstract High resolution imaging of the seafloor has been limited to fixed sensors and/or limited field-of-view instruments. As a result, our ability to characterize large areas of benthic habitat has relied on acoustic maps and photomosaics combined with point sampling. In addition, the response of motile epibenthos and demersal fish to habitat patches, structure and disturbance has been largely inferred or based on disruptive sampling and manipulative experiments. Direct quantitative observation of large areal variation in these factors is possible through a combination of traditional video census techniques with high resolution optical imaging of the seafloor. Laser Line Scan Systems (LLSS) are capable of imaging continuous swaths of the seafloor from 3 to 15 m wide at speeds up to 5 km/h. Image quality is dependent on system performance and turbidity but can exceed limits required to distinguish benthic habitats and census undisturbed fish and epibenthos. This areal coverage rate (1 km/day) is several orders of magnitude higher than video sleds and can complement high resolution acoustic surveys (multibeam or side scan). We present results from several applications of these systems for assessment of benthic resources and disturbance in turbid estuarine environments.

Chemical stability of capped dredged material disposal mounds in Long Island sound, USA

Abstract Geochemical analysis and visual inspection of cores collected from capped dredged material mounds revealed that in many cores, cap material was clearly distinguishable, both visually and chemically, from mound material. Contaminated dredged sediments were disposed in Long Island Sound eleven and seven years prior to sampling, and capped with uncontaminated dredged sediments. Core data provided no conclusive evidence of physical disturbance of, or chemical migration from, the contaminated mound sediments. Obvious chemical gradients of contaminant concentrations, which we propose are indicators of chemical migration, were not detected in the cores. Heterogeneity of the cap and mound sediments in some cores made the interface less distinct. We postulate that the preservation of spatial variability of sediment texture and associated contaminants observed within dredged material mounds is a result of the dredging process. Preservation of the textural and contaminant history of dredged sediments within...

Plan-view photos, benthic grabs, and sediment-profile images: using complementary techniques to assess response to seafloor disturbance.

A monitoring survey was conducted in July 2005 at the Rhode Island Sound Disposal Site (RISDS) as part of the Disposal Area Monitoring System (DAMOS) program. The survey included the collection of sediment-profile and plan-view images, and benthic biology grabs. Each of these techniques provides a different, yet complementary perspective on benthic community conditions. These complementary techniques aided in the assessment of the benthic recovery process within RISDS following the placement of dredged material from the Providence River and Harbor Maintenance Dredging Project (PRHMDP). Based on observed patterns of physical, chemical, and biological responses of seafloor environments to dredged material disposal activity it was expected that the benthic community within RISDS would be in an intermediate phase of recolonization (Stage II). Results of the 2005 RISDS survey indicated that in the six months since disposal activities at RISDS had concluded, the biological community at RISDS was recovering relatively rapidly and Stages II and III infauna were present throughout the region.

Biology and Ecology of Long Island Sound

Many compelling management issues in Long Island Sound (LIS) focus on how organisms respond to stresses such as commercial and recreational harvesting, eutrophication, hypoxia, habitat degradation, invasion of non-native species, ocean acidification, and climate change. In order to address these complex problems, we must first understand the factors controlling biological processes and how organisms interact ecologically. This chapter provides an overview of the major groups of organisms occupying the dominant habitats of LIS.