Posts Tagged 'echinoderms'

Evaluating the promise and pitfalls of a potential climate change–tolerant sea urchin fishery in southern California

Marine fishery stakeholders are beginning to consider and implement adaptation strategies in the face of growing consumer demand and potential deleterious climate change impacts such as ocean warming, ocean acidification, and deoxygenation. This study investigates the potential for development of a novel climate changetolerant sea urchin fishery in southern California based on Strongylocentrotus fragilis (pink sea urchin), a deep-sea species whose peak density was found to coincide with a current trap-based spot prawn fishery (Pandalus platyceros) in the 200–300-m depth range. Here we outline potential criteria for a climate changetolerant fishery by examining the distribution, life-history attributes, and marketable qualities of S. fragilis in southern California. We provide evidence of seasonality of gonad production and demonstrate that peak gonad production occurs in the winter season. S. fragilis likely spawns in the spring season as evidenced by consistent minimum gonad indices in the spring/summer seasons across 4 years of sampling (2012–2016). The resiliency of S. fragilis to predicted future increases in acidity and decreases in oxygen was supported by high species abundance, albeit reduced relative growth rate estimates at water depths (485–510 m) subject to low oxygen (11.7–16.9 µmol kg−1) and pHTotal (<7.44), which may provide assurances to stakeholders and managers regarding the suitability of this species for commercial exploitation. Some food quality properties of the S. fragilis roe (e.g. colour, texture) were comparable with those of the commercially exploited shallow-water red sea urchin (Mesocentrotus franciscanus), while other qualities (e.g. 80% reduced gonad size by weight) limit the potential future marketability of S. fragilis. This case study highlights the potential future challenges and drawbacks of climate-tolerant fishery development in an attempt to inform future urchin fishery stakeholders.

Continue reading ‘Evaluating the promise and pitfalls of a potential climate change–tolerant sea urchin fishery in southern California’

Population biology of the sea star Anasterias minuta (Forcipulatida: Asteriidae) threatened by anthropogenic activities in rocky intertidal shores of San Matías Gulf, Patagonia, Argentina

 In Patagonian coastal areas, intertidal benthic communities are exposed to extreme physical conditions. The interaction between harsh environment and anthropogenic pressure can generate changes in population biology of marine invertebrates, like density and reproduction. The oral brooding sea star Anasterias minuta is a key organism in food chains of Atlantic Patagonian rocky intertidals, hence changes on its population structure can negatively affect shore communities. We studied the population biology of A. minuta and assess the effect of environmental parameters and anthropogenic activities on its population on rocky intertidal shores of San Matías Gulf, Patagonia, Argentina. Seasonal sea surface temperature, pH, salinity, water velocity, desiccation rate, boulders density, and anthropogenic influence (tourists and octopus fishermen) were recorded. In sites with less tourist influence and high refuge, an increase in density was recorded, especially during the summer. Brooding individuals were found in fall and winter, while feeding individuals were observed in all seasons (12 different prey, mainly the molluscs Tegula patagonica and Perumytilus purpuratus). Environmental variables such as boulders density and water velocity were the most important predictor of variation in population structure. Tourism and pH were the most important variables negatively correlated with density.

Continue reading ‘Population biology of the sea star Anasterias minuta (Forcipulatida: Asteriidae) threatened by anthropogenic activities in rocky intertidal shores of San Matías Gulf, Patagonia, Argentina’

Repeated measurement of MO2 in small aquatic organisms: a manual intermittent flow respirometer using off-the-shelf components

Measurement of rates of oxygen consumption (MO2) in small aquatic embryos or larvae (< 1mm) in response to altered environmental conditions has traditionally been challenging. Here, using modifications of a commercially available fluorescent optode flow-through cell (FTC: PreSens{trade mark, serif} FTC-PSt3) and routine laboratory supplies (syringes, stopcocks, tubing), we have constructed a manual intermittent flow respirometer (MIFR) that allows measurement of MO2 in small numbers of individuals when sequentially exposed to different environmental conditions (e.g. changes in seawater pH) through a gravity-driven media replacement perfusion system. We first show that the FTC can be used in ‘static’ mode while incubating small numbers of embryos/larvae contained within the planar oxygen sensor (POS) chamber with Nitex filters. We then demonstrate the use of the MIFR by exposing larval echinoderms (Fellaster zelandiae, Evechinus chloroticus, Centrostephanus rodgersii) to seawater equilibrated with elevated CO2, and measured MO2 during acute and chronic exposure to hypercapnia. This MIFR method will allow investigators to address questions regarding the respiratory physiology of small aquatic animals, such as the thresholds for metabolic depression in embryonic and larval forms.

Continue reading ‘Repeated measurement of MO2 in small aquatic organisms: a manual intermittent flow respirometer using off-the-shelf components’

Species interactions can shift the response of a maerl bed community to ocean acidification and warming (update)

Predicted ocean acidification and warming are likely to have major implications for marine organisms, especially marine calcifiers. However, little information is available on the response of marine benthic communities as a whole to predicted changes. Here, we experimentally examined the combined effects of temperature and partial pressure of carbon dioxide (pCO2) increases on the response of maerl bed assemblages, composed of living and dead thalli of the free-living coralline alga Lithothamnion corallioides, epiphytic fleshy algae, and grazer species. Two 3-month experiments were performed in the winter and summer seasons in mesocosms with four different combinations of pCO2 (ambient and high pCO2) and temperature (ambient and +3 °C). The response of maerl assemblages was assessed using metabolic measurements at the species and assemblage scales. This study suggests that seasonal variability represents an important driver influencing the magnitude and the direction of species and community response to climate change. Gross primary production and respiration of assemblages was enhanced by high pCO2 conditions in the summer. This positive effect was attributed to the increase in epiphyte biomass, which benefited from higher CO2 concentrations for growth and primary production. Conversely, high pCO2 drastically decreased the calcification rates in assemblages. This response can be attributed to the decline in calcification rates of living L. corallioides due to acidification and increased dissolution of dead L. corallioides. Future changes in pCO2 and temperature are likely to promote the development of non-calcifying algae to the detriment of the engineer species L. corallioides. The development of fleshy algae may be modulated by the ability of grazers to regulate epiphyte growth. However, our results suggest that predicted changes will negatively affect the metabolism of grazers and potentially their ability to control epiphyte abundance. We show here that the effects of pCO2 and temperature on maerl bed communities were weakened when these factors were combined. This underlines the importance of examining multi-factorial approaches and community-level processes, which integrate species interactions, to better understand the impact of global change on marine ecosystems.

Continue reading ‘Species interactions can shift the response of a maerl bed community to ocean acidification and warming (update)’

Variability in larval gut pH regulation defines sensitivity to ocean acidification in six species of the Ambulacraria superphylum

The unusual rate and extent of environmental changes due to human activities may exceed the capacity of marine organisms to deal with this phenomenon. The identification of physiological systems that set the tolerance limits and their potential for phenotypic buffering in the most vulnerable ontogenetic stages become increasingly important to make large-scale projections. Here, we demonstrate that the differential sensitivity of non-calcifying Ambulacraria (echinoderms and hemichordates) larvae towards simulated ocean acidification is dictated by the physiology of their digestive systems. Gastric pH regulation upon experimental ocean acidification was compared in six species of the superphylum Ambulacraria. We observed a strong correlation between sensitivity to ocean acidification and the ability to regulate gut pH. Surprisingly, species with tightly regulated gastric pH were more sensitive to ocean acidification. This study provides evidence that strict maintenance of highly alkaline conditions in the larval gut of Ambulacraria early life stages may dictate their sensitivity to decreases in seawater pH. These findings highlight the importance of identifying and understanding pH regulatory systems in marine larval stages that may contribute to substantial energetic challenges under near-future ocean acidification scenarios.

Continue reading ‘Variability in larval gut pH regulation defines sensitivity to ocean acidification in six species of the Ambulacraria superphylum’

Dissolution of abiogenic and biogenic calcium carbonate under ocean acidification conditions

Under ocean acidification conditions, the chemistry of the seawater will change including a decrease in pH, a decrease in carbonate ion concentration and a decrease in the calcium carbonate saturation state of the water (Ω). This has implications for solid marine calcium carbonates including calcifying organisms and carbonate sediments. The dissolution kinetics of marine carbonates are poorly understood, therefore modelling of the future ocean under ocean acidification scenarios is hampered. The goal of this research was to provide an increased understanding of the kinetics of marine carbonate dissolution, including dependence of the dissolution rate of calcium carbonate mineral phases (calcite, calcite-aragonite, low Mg-calcite) on conditions relevant to ocean acidification, and then to apply this to biogenic samples (Pāua, kina and oyster). The effects of saturation state (Ω), surface area, and temperature were studied. Two methods were refined and used to collect and analyze the dissolution data – a pH-stat method and a pH free-drift method, with manipulation of the carbonate chemistry by addition of NaHCO3 and HCl. A LabVIEW® based program was developed for instrument control and automation and for data acquisition. The empirical equation R = k(1-Ω)n, was used to determine the reaction rates (R), the rate constants (k) and the reaction orders (n) for the each of the mineral phases and shellfish species.

Continue reading ‘Dissolution of abiogenic and biogenic calcium carbonate under ocean acidification conditions’

Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios

Coastal hypoxia is a problem that is predicted to increase rapidly in the future. At the same time we are facing rising atmospheric CO2 concentrations, which are increasing the pCO2 and acidity of coastal waters. These two drivers are well studied in isolation however; the coupling of low O2 and pH is likely to provide a more significant respiratory challenge for slow moving and sessile invertebrates than is currently predicted. The Gullmar Fjord in Sweden is home to a range of habitats such as sand and mud flats, seagrass beds, exposed and protected shorelines, and rocky bottoms. Moreover, it has a history of both natural and anthropogenically enhanced hypoxia as well as North Sea upwelling, where salty water reaches the surface towards the end of summer and early autumn. A total of 11 species (Crustacean, Chordate, Echinoderm and Mollusc) of these ecosystems were exposed to four different treatments (high/low oxygen and low/high CO2; varying pCO2 of 450 and 1300 ppm and O2 concentrations of 2–3.5 and 9–10 mg L−1) and respiration measured after 3 and 6 days, respectively. This allows us to evaluate respiration responses of species of contrasting habitats and life-history strategies to single and multiple stressors. Results show that the responses of the respiration were highly species specific as we observed both synergetic as well as antagonistic responses, and neither phylum nor habitat explained trends in respiratory responses. Management plans should avoid the generalized assumption that combined stressors will results in multiplicative effects and focus attention on alleviating hypoxia in the region.
Continue reading ‘Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios’

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Ocean acidification in the IPCC AR5 WG II

OUP book