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Environmental ecotoxieology studies use sea urchin skeletal components to examine potential changes in concentrations of trace element pollutants. To date, such studies have not considered how body size may alter the innate concentrations of trace elements in a given skeletal component. The present study examines this issue using the common nearshore sea urchin Lytechinus variegatus as a model species. Concentrations of barium, boron, manganese, and strontium was measured using ICP-OES in three major skeletal subcomponents (Aristotle's lantern, spines, and test) of individuals' representative of live size cohorts spanning the late juvenile to adult. Concentrations of three of the four elements, barium, boron, and manganese, varied significantly with body size, largely declining as test diameter increased. As concentrations of trace elements was normalized to skeletal mass originated from collections of individuals in pristine bay waters and from the same population at the same time, differences in trace element concentrations are innately ontogenetic. Accordingly, future ecotoxicological studies employing skeletal subcomponents of sea urchins should consider the relationship between trace element concentration and body size when designing sampling regimes. KEY WORDS: Lytechinus variegatus, sea urchin, skeletal subcomponent, trace element, environmental ecotoxieology, INTRODUCTION Regular echinoids are key members of nearshore marine communities encompassing such diverse marine habitats as sea-grass beds, rocky intertidal platforms, tide pools, and macroalgal forests (Lawrence 2013). Due to [...]

Benthic assemblages of the Antarctic continental shelf are dominated by sessile and slow-moving, epifaunal invertebrates. This community structure persists because shell-crushing (durophagous) predators are absent or ecologically insignificant in shelf habitats. Durophagous teleosts, elasmobranchs, and crustaceans have been excluded by cold waters over the Antarctic shelf for millions of years. Now, as shallow waters warm rapidly, predatory king crabs (Lithodidae) living in the upper bathyal zone could emerge onto the shelf and into nearshore habitats. To assess the potential for a bathymetric expansion, we genetically inferred the historical demography of a population of the most abundant durophagous predator found in deep water off the western Antarctic Peninsula: the lithodid Paralomis birsteini Macpherson. Analysis of mitochondrial DNA sequences from crabs sampled at 1200–1400 m depth on the slope off Marguerite Bay suggests this population has expanded twice over the past 132,000 years. Those expansions were possibly coincident with episodes of climatic warming in Antarctica and elsewhere, raising the possibility of a third expansion in response to anthropogenic climate change.

Ontogenetic allometric analyses can provide novel insights into aspects of evolution, ecology, and conservation. The present study exploits a model sea urchin to evaluate the ontogenetic allometry of skeletal defense and feeding efficiency. Individuals of Lytechinus variegatus were sampled from St. Joseph Bay. FL, and a range of different-sized late juvenile to adult individuals were weighed, measured, and dissected into skeletal components. Skeletal defense was evaluated by examining whole-body wet mass versus primary spine density (number/cnr). length (mm), breakage strength (iV), and magnesium calcite levels (%). Feeding efficiency was indirectly inferred from the relationship between whole-body wet mass versus whole lantern dry weight and magnesium calcite content. It was found that between the late juvenile to adult growth phase. L. variegatus displays nonlinear and isometric scaling between body size and various metrics of skeletal spine defense. Intriguingly, most metrics of spine defense against predators displayed a nonsignificant, body-size-independent relationship. indicating L. variegatus invests heavily in spine defenses at an early age. In contrast, hyperallometric scaling best described the relationship between body size and lantern size (feeding efficiency) reflecting the potential importance of elevating food intake with increasing age. KEY WORDS: Lytechinus variegatus, ontogeny, allometry, echinoid, skeletal defense, feeding efficiency, INTRODUCTION Investigations of allometry in marine organisms can provide valuable insights into life history strategies and the adaptive significance of body form and proportionality as well as provide insights relevant [...]

Fleshy macroalgae dominate the hard bottom, shallow waters along the Western Antarctic Peninsula (WAP). Although there are numerous reports on their ecology, geographic distribution, and to a lesser extent, vertical (depth) distribution in the northern portions of the WAP, much less is known farther south along the central portion of the WAP. Here we provide the first report of the vertical distributions of brown and red fleshy macroalgae in this region based on scuba-derived collections at 14 study sites between southern Anvers Island (64.8°S, 64.4°W) in the north and central Marguerite Bay (68.7°S, 67.5°W) in the south. Although several overstory brown macroalgal species that can be common along the northern WAP including Desmarestia anceps and Cystosphaera jacquinotii are mostly absent from the central WAP, the vertical distributions of the brown macroalgae Desmarestia menziesii and Himantothallus grandifolius are similar to the northern WAP even though their percent cover is much lower. Likewise, the vertical distribution of the 14 most widespread red macroalgae, where they occur, mirrored those known from the northern part of the WAP even though macroalgal cover, biomass, and total species richness declined markedly to the south across this region due to increasing sea ice concentrations. [ABSTRACT FROM AUTHOR]

As mean global temperatures continue to rise, regional seawater temperature measurements have revealed that some geographic areas are warming faster than others. One region that is experiencing particularly rapid warming is the western Antarctic Peninsula. Previous studies investigating direct effects of warming on Antarctic marine invertebrates have established that small increases in temperature can have significant impacts on aspects of behavior, physiology, and growth rates in these largely stenothermal organisms. To investigate how warming may impact feeding preferences of an ecologically important mesograzer on macroalgae of the Antarctic Peninsula, we examined the impacts of exposure to acute elevated temperature on the ecologically important omnivorous amphipod Gondogeneiea antarctica (Chevreux) at Palmer Station, Antarctica (64°46/S, 64°03/W) in April-May 2011. Amphipods were exposed to 1.5°C (mean monthly upper summer temperature) or 3.5°C (representative of current transient summer temperature peaks and projected mean for 2100) for a 24 h period. These amphipods were then used in choice-feeding assays with artificial food containing chemical extracts from six species of sympatric macroalgae known to produce feeding deterrents. We found that during acute exposure to elevated temperature (+2.0°C), amphipods lost their feeding preferences in assays with artificial foods containing lipophilic (one macroalga), hydrophilic (three macroalgae), or combined lipophilic/hydrophilic (one macroalga) extracts. Our findings suggest that increased frequency in transient peaks and longer-term upward trends in ambient summer seawater temperature have the potential to alter feeding preferences in a common mesograzer that could influence macroalgal communities that dominate benthic communities along the western Antarctic Peninsula., Introduction The rapid warming and concomitant reductions in the extent and duration of the annual sea ice (Martinson et al. 2008) make studies of marine organismal response to warming along [...]