J. Mar. Sci. Eng.2015, 3(2), 267-275; doi:10.3390/jmse3020267 (registering DOI) - published 22 May 2015 Show/Hide Abstract
Abstract: Numerous anthropogenic factors represent environmental threats to Gulf Coast wetland ecosystems and associated fauna. American alligators (Alligator mississippiensis) have been subject to long-term management and used as ecological and physiological indicators of habitat quality in response to anthropogenic events and stochastic natural disasters. The present study monitored heterophil to lymphocyte ratios (an indicator of stress), in American alligators in a Louisiana intermediate marsh from 2009 to 2011, a time period that coincides with an oil inundation event that occurred in 2011. Sixteen alligators were observed and processed morphometrically (total length, snout-vent length and body mass). Heterophil to lymphocyte ratios were negatively correlated with size, suggesting larger American alligators were physiologically more resilient to the disturbance, more able to actively avoid these poor conditions, or are less affected by localized disturbance.
J. Mar. Sci. Eng.2015, 3(2), 240-266; doi:10.3390/jmse3020240 - published 19 May 2015 Show/Hide Abstract
Abstract: The annual production from global aquaculture has increased rapidly from 2.6 million tons or 3.9% of the total supply of fish, shellfish and mollusks in 1970, to 66.7 million tons or 42.2% in 2012, while capture fisheries have more or less leveled out at about 90 million tons per year since the turn of the century. Consequently, the future seafood supply is likely to depend on a further increase of aquaculture production. Unlike terrestrial animal farming, less than 10% of the aquaculture production comes from domesticated and selectively bred farm stocks. This situation has substantial consequences in terms of poorer resource efficiency, poorer product quality and poorer animal welfare. The history of biological and technical challenges when establishing selective breeding programs for aquaculture is discussed, and it is concluded that most aquaculture species may now be domesticated and improved by selection. However, the adoption of selective breeding in aquaculture is progressing slowly. This paper reports on a study carried out in 2012 to identify key issues to address in promoting the development of genetically improved aquaculture stocks. The study involved semi structured interviews of 34 respondents from different sectors of the aquaculture society in East and Southeast Asia, where 76% of the global aquaculture production is located. Based on the interviews and literature review, three key factors are identified: (i) long-term public commitment is often needed for financial support of the breeding nucleus operation (at least during the first five to ten generations of selection); (ii) training at all levels (from government officers and university staff to breeding nucleus and hatchery operators, as well as farmers); and (iii) development of appropriate business models for benefit sharing between the breeding, multiplier and grow-out operators (whether being public, cooperative or private operations). The public support should be invested in efforts of selective breeding on the most important and highest volume species, which may not be a priority for investment by private breeders due to, for instance, long generation intervals and delays in return to investment.
J. Mar. Sci. Eng.2015, 3(2), 216-239; doi:10.3390/jmse3020216 - published 6 May 2015 Show/Hide Abstract
Abstract: The impact of global climate change on coral reefs is expected to be most profound at the sea surface, where fertilization and embryonic development of broadcast-spawning corals takes place. We examined the effect of increased temperature and elevated CO2 levels on the in vitro fertilization success and initial embryonic development of broadcast-spawning corals using a single male:female cross of three different species from mid- and high-latitude locations: Lyudao, Taiwan (22° N) and Kochi, Japan (32° N). Eggs were fertilized under ambient conditions (27 °C and 500 μatm CO2) and under conditions predicted for 2100 (IPCC worst case scenario, 31 °C and 1000 μatm CO2). Fertilization success, abnormal development and early developmental success were determined for each sample. Increased temperature had a more profound influence than elevated CO2. In most cases, near-future warming caused a significant drop in early developmental success as a result of decreased fertilization success and/or increased abnormal development. The embryonic development of the male:female cross of A. hyacinthus from the high-latitude location was more sensitive to the increased temperature (+4 °C) than the male:female cross of A. hyacinthus from the mid-latitude location. The response to the elevated CO2 level was small and highly variable, ranging from positive to negative responses. These results suggest that global warming is a more significant and universal stressor than ocean acidification on the early embryonic development of corals from mid- and high-latitude locations.
J. Mar. Sci. Eng.2015, 3(2), 193-215; doi:10.3390/jmse3020193 - published 5 May 2015 Show/Hide Abstract
Abstract: The present study investigates the performances of the three-dimensional multicomponent hydro-sedimentary model ROMS (Regional Ocean Modeling System) to predict near-surface suspended sediment concentrations (SSC) in the English Channel (western Europe). Predictions are assessed against satellite-retrieved observations from raw MODIS and MERIS images for the year 2008 characterized by the highest availability of cloud-free data. Focus is put on improvements obtained with: (1) SSC inputs at the open boundaries; and (2) simple parameterizations of the settling velocity and the critical shear stress. Sensitivity studies confirm the importance of the advection of fine-grained suspended sediments in the central waters of the English Channel exhibiting benefits of refined SSC estimations along the sea boundaries. Improvements obtained with modified formulations of the settling velocity and the critical shear stress finally suggest possible seasonal influences of biological activity and thermal stratification on near-surface SSC.
J. Mar. Sci. Eng.2015, 3(2), 175-192; doi:10.3390/jmse3020175 - published 23 April 2015 Show/Hide Abstract
Abstract: Epigenetic marks affecting the expression of genes are triggered by environmental stimuli, can persist throughout life or across multiple generations and can affect an individuals phenotype. In recent years there has been a revival of interest about the possible role of epigenetics in affecting complex or quantitative traits. This growing interest is partly driven by the increasing affordability of ultra-high throughput sequencing methods for studying the epigenome. In this review we focus on some of the possible applications of epigenetic knowledge to the improvement of aquaculture. DNA methylation, in which a methyl group is added to the C5 carbon residue of a cytosine by DNA methyltransferase, has been the most widely studied epigenetic mechanism to date, and methods used to obtain and analyse genome-wide DNA methylation data are outlined. The influence of epigenetic processes on the estimation of breeding values and accuracy of genomic selection for genetic improvement of aquatic species is explored. The possibility of tightly controlling nutritional stimuli found to affect epigenetic processes in order to tailor the development of fish for aquaculture is also discussed. Complex experiments will be required in order to gain a better understanding of the role of epigenetics in affecting quantitative traits in fish.
J. Mar. Sci. Eng.2015, 3(2), 154-174; doi:10.3390/jmse3020154 - published 15 April 2015 Show/Hide Abstract
Abstract: Clay minerals have previously been used to mitigate algal blooms because of their ability to flocculate algal cells or remove nutrients, but also offer considerable potential to remove ichthyotoxins. When a barramundi farm in tropical Australia suffered substantial fish mortalities due to a bloom of the ichthyotoxic haptophyte Prymnesium parvum, the farm manager decided to manipulate pond water N:P ratios through removal of phosphorus by the addition of lanthanum-modified bentonite clay (Phoslock™) to successfully mitigate ichthyotoxic effects. We conducted Prymnesium culture experiments under a range of N:P ratios, screening 14 different clays (two zeolites, four kaolins, six bentonites and two types of Korean loess) at pH 7 and 9 for cell flocculation and removal of ichthyotoxicity assessed with the RTgill-W1 cell line assay. Application of Phoslock™ to cultures grown at different N:P effectively removed 60%–100% of water-soluble toxicity of live Prymnesium (dependent on nutritional status). While most clays efficiently flocculated Prymnesium cells (≥80% removal), cell removal proved a poor predictor of ichthyotoxin adsorption. Extensive clay screening revealed that at elevated pH, as commonly associated with dense algal blooms, most clays either exacerbated ichthyotoxicity or exhibited significantly reduced toxin adsorption. Interpretation of changes in clay zeta potential at pH 7 and 9 provided valuable insight into clay/ichthyotoxin interactions, yet further research is required to completely understand the adsorption mechanisms. Bentonite-type clays proved best suited for ichthyotoxin removal purposes (100% removal at ecologically relevant pH 9) and offer great potential for on-farm emergency response.