Comparative analysis of marine ecosystems: international production modelling workshop.

Understanding the drivers that dictate the productivity of marine ecosystems continues to be a globally important issue. A vast literature identifies three main processes that regulate the production dynamics of such ecosystems: biophysical, exploitative and trophodynamic. Exploring the prominence among this 'triad' of drivers, through a synthetic analysis, is critical for understanding how marine ecosystems function and subsequently produce fisheries resources of interest to humans. To explore this topic further, an international workshop was held on 10-14 May 2010, at the National Academy of Science's Jonsson Center in Woods Hole, MA, USA. The workshop compiled the data required to develop production models at different hierarchical levels (e.g. species, guild, ecosystem) for many of the major Northern Hemisphere marine ecosystems that have supported notable fisheries. Analyses focused on comparable total system biomass production, functionally equivalent species production, or simulation studies for 11 different marine fishery ecosystems. Workshop activities also led to new analytical tools. Preliminary results suggested common patterns driving overall fisheries production in these ecosystems, but also highlighted variation in the relative importance of each among ecosystems.

Demographic responses to multigeneration cadmium exposure in two strains of the freshwater gastropod, Biomphalaria glabrata.

A life table response experiment (LTRE) was used to quantify the population-level effects of continuous, multigeneration cadmium exposure on two strains of the freshwater gastropod, Biomphalaria glabrata: the parasite-resistant BS90 and parasite-susceptible NMRI strains. Snails were exposed to waterborne cadmium for three consecutive generations. Survival, growth, and reproduction were measured empirically and incorporated into a stage-based, deterministic population model. Cadmium significantly affected hatching success, time to maturity, and juvenile and adult survival in both strains. There were significant effects of generation on fecundity, hatching success, time to maturity and juvenile survival in NMRI, and time to maturity and adult survival in BS90. Cadmium significantly affected the population growth rate, lambda, in BS90. Cadmium, generation, and the cadmium x generation interaction had significant effects on lambda in NMRI. At the high cadmium exposure, lambda for NMRI showed a decrease from generation 1 to generation 2, followed by an increase from generation 2 to generation 3. The lambda value in high-cadmium BS90 steadily decreased over the three generations, while NMRI at this same concentration was similar to the controls. The results indicate that strain-specific differences in response to multigeneration cadmium exposure are evident in B. glabrata. Moreover, effects seen in the first generation are not necessarily indicative of effects in subsequent generations. Changes in lambda over the course of the three-generation exposure suggest that acclimation and/or adaptation to cadmium may have occurred, particularly in NMRI at the high cadmium exposure level.

Winter is (not) coming: Warming temperatures will affect the overwinter behavior and survival of blue crab.

Understanding how increases in water temperature may affect winter dormancy period duration and overwinter survival are important for the effective conservation and management of estuarine species in the face of a warming climate. In this study, we determined the length of the overwintering period and the probability of overwinter survival of blue crab (Callinectes sapidus), an ecologically and economically important estuarine crustacean. Overwintering period length and probability of overwinter survival were determined using projected water temperatures up to the year 2100, derived from a harmonic model that utilized air temperatures from multi-model ensemble of regional-scale climate projections. Our estimates of warming water temperatures by 2100 in Chesapeake Bay indicate that winters will be up to 50% shorter and overwinter survival will increase by at least 20% compared to current conditions. The warmer conditions will lead to faster and prolonged seasonal growth, which, when combined with lower winter mortality, will lead to increased population productivity. The level of expression of this increased productivity will depend on the response of other elements of the Chesapeake Bay food web, as well as possible changes to fishery management policies over the same time period.

The effect of maternal exposure to contaminated sediment on the growth and condition of larval Fundulus heteroclitus.

We employed a factorial laboratory experiment to determine the single and combined effect of maternal and larval exposure to contaminated sediment from Elizabeth River, Virginia, a site contaminated with high concentrations of multiple pollutants. Females were exposed to either reference or contaminated sediment and the larvae from both groups of mothers were in turn transferred to either reference or contaminated sediment. We found a strong maternal influence on yolk area, length and RNA:DNA ratio at hatch. Further, the maternal exposure significantly influenced growth rate and RNA:DNA ratios of larvae 14 days after hatch and was a more important factor in determining these endpoints than larval exposure. We found that after 14 days larvae were larger and had higher survivorship when the maternal and larval exposures were the same. There also was no statistical difference with respect to growth and condition between larvae that had hatched from exposed mothers and remained in contaminated water and larvae that had hatched from reference mothers and were placed in either reference or contaminated sediment. However, larvae that hatched from exposed mothers and then were switched to reference sediment had significantly lower growth, lower RNA:DNA ratios, and were smaller despite being large at hatch size, indicating that there are fitness trade-offs in exchange for apparent resistance to contaminants which are provided by the mother. Maternal effects add complexity to ecotoxicological research and should be incorporated into studies to predict population level responses more realistically.

Position paper: The potential role of optical biopsy in the study and diagnosis of environmental enteric dysfunction.

Environmental enteric dysfunction (EED) is a disease of the small intestine affecting children and adults in low and middle income countries. Arising as a consequence of repeated infections, gut inflammation results in impaired intestinal absorptive and barrier function, leading to poor nutrient uptake and ultimately to stunting and other developmental limitations. Progress towards new biomarkers and interventions for EED is hampered by the practical and ethical difficulties of cross-validation with the gold standard of biopsy and histology. Optical biopsy techniques - which can provide minimally invasive or noninvasive alternatives to biopsy - could offer other routes to validation and could potentially be used as point-of-care tests among the general population. This Consensus Statement identifies and reviews the most promising candidate optical biopsy technologies for applications in EED, critically assesses them against criteria identified for successful deployment in developing world settings, and proposes further lines of enquiry. Importantly, many of the techniques discussed could also be adapted to monitor the impaired intestinal barrier in other settings such as IBD, autoimmune enteropathies, coeliac disease, graft-versus-host disease, small intestinal transplantation or critical care.

Population-level responses to long-term cadmium exposure in two strains of the freshwater gastropod Biomphalaria glabrata: results from a life-table response experiment.

A life-table response experiment was conducted to ascertain the demographic effects of low-level cadmium exposure on two strains, BS90 and NMRI, of the freshwater gastropod Biomphalaria glabrata. Snails were exposed to cadmium continuously from the embryonic stage through adulthood. Results indicated that cadmium significantly affected a number of individual-based parameters, including %hatch, juvenile survival, and adult survival in both strains. Also, fecundity and time to maturity were significantly affected in the NMRI strain. A stage-based, deterministic, population model indicated that population growth rate (lambda) was significantly affected by cadmium. Elasticity analysis indicated that juvenile survival, in general, had the greatest contribution to lambda. Decomposition analysis indicated that the effects of cadmium on the juvenile stage in BS90 and the embryonic stage in NMRI contributed most to cadmium-induced changes in lambda. The BS90 strain was more sensitive to cadmium toxicity than NMRI. Moreover, the two strains differed in pattern of response with different aspects of their respective life histories contributing to cadmium-induced changes in lambda. Comparisons were also made between the main model, based on a Z transformation of the life-cycle graph, and more commonly used matrix models.

Comment on "Impacts of biodiversity loss on ocean ecosystem services".

Worm et al. (Research Articles, 3 November 2006, p. 787) reported an increasing proportion of fisheries in a "collapsed" state. We show that this may be an artifact of their definition of collapse as a fixed percentage of the maximum and that an increase in the number of managed fisheries could produce similar patterns as an increase in fisheries with catches below 10% of the maximum.