Posts Tagged 'North Pacific'

Plastic responses of bryozoans to ocean acidification

Phenotypic plasticity has the potential to allow organisms to respond rapidly to global environmental change, but the range and effectiveness of these responses are poorly understood across taxa and growth strategies. Colonial organisms might be particularly resilient to environmental stressors, as organizational modularity and successive asexual generations can allow for distinctively flexible responses in the aggregate form. We performed laboratory experiments to examine the effects of increasing dissolved carbon dioxide (i.e. ocean acidification) on the colonial bryozoan Celleporella cornuta sampled from two source populations within a coastal upwelling region of the northern California coast. Bryozoan colonies were remarkably plastic under these carbon dioxide (CO2) treatments. Colonies raised under high CO2 grew more quickly, investing less in reproduction and producing lighter skeletons when compared to genetically identical clones raised under current atmospheric values. Bryozoans held in high CO2 conditions also changed the Mg/Ca ratio of skeletal calcite and increased the expression of organic coverings in new growth, which may serve as protection against acidified water. We also observed strong differences between populations in reproductive investment and organic covering reaction norms, consistent with adaptive responses to persistent spatial variation in local oceanographic conditions. Our results demonstrate that phenotypic plasticity and energetic trade-offs can mediate biological responses to global environmental change, and highlight the broad range of strategies available to colonial organisms.

Continue reading ‘Plastic responses of bryozoans to ocean acidification’

Acidification mediated by a river plume and coastal upwelling on a fringing reef at the east coast of Hainan Island, Northern South China Sea

We investigated the dynamics of carbonate system which was greatly modulated by a river plume and coastal upwelling in July 2014 and July 2015 at the east coast of Hainan Island where a fringing reef distributes inshore. By using a three end-member mixing model, we semiquantitatively estimated the removal of dissolved inorganic carbon (DIC) mediated by biological production in the river plume and upwelled water to be 13 ± 17 and 15 ± 16 μmol kg−1, respectively. The enhanced organic production was mainly responsible for these DIC consumptions in both two regimes, however, nearly a half of DIC removal was attributed to biocalcification in the plume system while it was negligible in the upwelling system. Furthermore, the modeled results over reefs revealed that river plume and coastal upwelling were two major threats of acidification to coral communities at the east coast of Hainan Island during cruises. In comparison, the biological contribution to acidification was limited for balancing between organic production and biocalcification during July 2014 cruise, whereas the acidification was greatly intensified by organic degradation during July 2015 cruise. It was verified that naturally local acidification (physical and biological processes) played a major role in great pH decreases on a short-term scale, leading to coastal waters more vulnerable to anthropogenic “ocean acidification” (uptake of atmospheric CO2) by reducing buffering capacity of waters. Finally, effects of acidification associated with other local threats on a fringing reef were further depicted with a conceptual model.

Continue reading ‘Acidification mediated by a river plume and coastal upwelling on a fringing reef at the east coast of Hainan Island, Northern South China Sea’

Using mineralogy and higher-level taxonomy as indicators of species sensitivity to pH: a case-study of Puget Sound

Information on ecosystem sensitivity to global change can help guide management decisions. Here, we characterize the sensitivity of the Puget Sound ecosystem to ocean acidification by estimating, at a number of taxonomic levels, the direct sensitivity of its species. We compare sensitivity estimates based on species mineralogy and on published literature from laboratory experiments and field studies. We generated information on the former by building a database of species in Puget Sound with mineralogy estimates for all CaCO3-forming species. For the latter, we relied on a recently developed database and meta-analysis on temperate species responses to increased CO2. In general, species sensitivity estimates based on the published literature suggest that calcifying species are more sensitive to increased CO2 than non-calcifying species. However, this generalization is incomplete, as non-calcifying species also show direct sensitivity to high CO2 conditions. We did not find a strong link between mineral solubility and the sensitivity of species survival to changes in carbonate chemistry, suggesting that, at coarse scales, mineralogy plays a lesser role to other physiological sensitivities. Summarizing species sensitivity at the family level resulted in higher sensitivity scalar scores than at the class level, suggesting that grouping results at the class level may overestimate species sensitivity. This result raises caution about the use of broad generalizations on species response to ocean acidification, particularly when developing summary information for specific locations. While we have much to learn about species response to ocean acidification and how to generalize ecosystem response, this study on Puget Sound suggests that detailed information on species performance under elevated carbon dioxide conditions, summarized at the lowest taxonomic level possible, is more valuable than information on species mineralogy.

Continue reading ‘Using mineralogy and higher-level taxonomy as indicators of species sensitivity to pH: a case-study of Puget Sound’

Effect of CO2 on growth and toxicity of Alexandrium tamarense from the East China Sea, a major producer of paralytic shellfish toxins

Highlights

  • Strain of Alexandrium tamarense isolated from East China Seas, showed a significant response to elevated CO2 levels in growth and toxicity.
  • Strain ATDH grew faster and showed a larger density when exposed to elevated CO2 concentration, especially in the exponential period.
  • The concentration per cell of each PST derivate varied and eventually caused the cellular toxicity increased when exposed to higher pCO2.


Abstract

In recent decades, the frequency and intensity of harmful algal blooms (HABs), as well as a profusion of toxic phytoplankton species, have significantly increased in coastal regions of China. Researchers attribute this to environmental changes such as rising atmospheric CO2 levels. Such addition of carbon into the ocean ecosystem can lead to increased growth, enhanced metabolism, and altered toxicity of toxic phytoplankton communities resulting in serious human health concerns. In this study, the effects of elevated partial pressure of CO2 (pCO2) on the growth and toxicity of a strain of Alexandrium tamarense (ATDH) widespread in the East and South China Seas were investigated. Results of these studies showed a higher specific growth rate (0.31 ± 0.05 day−1) when exposed to 1000 μatm CO2, (experimental), with a corresponding density of (2.02 ± 0.19) × 107 cells L−1, that was significantly larger than cells under 395 μatm CO2(control). These data also revealed that elevated pCO2 primarily affected the photosynthetic properties of cells in the exponential growth phase. Interestingly, measurement of the total toxin content per cell was reduced by half under elevated CO2 conditions. The following individual toxins were measured in this study: C1, C2, GTX1, GTX2, GTX3, GTX4, GTX5, STX, dcGTX2, dcGTX3, and dcSTX. Cells grown in 1000 μatm CO2 showed an overall decrease in the cellular concentrations of C1, C2, GTX2, GTX3, GTX5, STX, dcGTX2, dcGTX3, and dcSTX, but an increase in GTX1 and GTX4. Total cellular toxicity per cell was measured revealing an increase of nearly 60% toxicity in the presence of elevated CO2 compared to controls. This unusual result was attributed to a significant increase in the cellular concentrations of the more toxic derivatives, GTX1 and GTX4.Taken together; these findings indicate that the A. tamarense strain ATDH isolated from the East China Sea significantly increased in growth and cellular toxicity under elevated pCO2 levels. These data may provide vital information regarding future HABs and the corresponding harmful effects as a result of increasing atmospheric CO2.

Continue reading ‘Effect of CO2 on growth and toxicity of Alexandrium tamarense from the East China Sea, a major producer of paralytic shellfish toxins’

Spatio-temporal variation of phytoplankton communities along a salinity and pH gradient in a tropical estuary (Brunei, Borneo, South East Asia)

Characterizing phytoplankton communities is essential to understanding the ecological functioning of pelagic marine systems. Nevertheless, our knowledge of phytoplankton communities is still inadequate for many tropical habitats, including estuaries. It is assumed that highly turbid tropical estuaries often experience acidification due to anthropogenic inputs, microbial degradation, run-off from acidic sulphate soils, and low buffer capacity characteristic for all estuarine systems. Here, we describe phytoplankton communities from the turbid, acidified, and euthrophised estuary of Brunei River (South East Asia). The four selected sampling stations represented gradients of salinity (0.4 – 28.5 PSU) and pH (5.87 – 8.06). A total of 26 microalgal families of phytoplankton (22 genera of diatoms, 7 of dinoflagellates, and 1 of ciliates) were recorded in the survey carried out over one year. The highest density was recorded at an intermediate station along the gradient (up to 9107 cells ml-1), whereas the lowest diversity was found at the least saline and most acidic station (7-1146 cells ml-1). Diatoms were a dominant component of the communities, with Nitzschia spp., Rhizosolenia spp., and Leptocylindrus sp. reaching the highest abundances. Salinity, pH and dissolved oxygen (DO) were positively correlated with the plankton abundances and typically declined landwards. Statistical analyses indicated that phytoplankton communities were strongly influenced by the effect of season (30 % of the total variance in phytoplankton data explained) and sampling site (20 %). The joint effect of pH and salinity and of pH and temperature explained 16.7 % and 17.5 % of the total observed variation, respectively.

Continue reading ‘Spatio-temporal variation of phytoplankton communities along a salinity and pH gradient in a tropical estuary (Brunei, Borneo, South East Asia)’

Assessment and management of cumulative impacts in California’s network of marine protected areas

In response to concerns about human impacts to coastal ecosystems, conservationists and practitioners are increasingly turning to networks of marine protected areas (MPAs). Although MPAs manage for fishing pressure, many species and habitats in MPAs remain exposed to a multitude of stressors, including stressors from global climate change and regional land- and ocean-based activities. To support the adaptive management of MPAs that are subject to multiple interacting stressors, coastal managers need to understand the potential impacts from other single and multiple stressors. To demonstrate how this can be done, we quantify and map cumulative impacts resulting from multiple stressors to California’s network of MPAs, using a widely available cumulative impacts mapping tool. Among individual stressors, those related to climate, including ocean acidification, UV radiation increases, and SST anomalies, were found to have the most intense impacts, especially on surface waters and in the rocky intertidal. Climate stressors are challenging to limit at the local MPA scale, but intense land- and ocean-based impacts that were found to affect a majority of MPAs, such as sediment increases, invasive species, organic pollutants and pollution from shipping and ports, may be more easily regulated at a regional or local scale. This is especially relevant for South and Central coast MPAs where these impacts are the greatest on beaches, tidal flats, and coastal marshes. Accounting for cumulative impacts from these and other stressors when developing monitoring and management plans in California and across the world, would help to improve the efficacy of MPAs.

Continue reading ‘Assessment and management of cumulative impacts in California’s network of marine protected areas’

Effects of elevated pCO2 on crab survival and exoskeleton composition depend on shell function and species distribution: a comparative analysis of carapace and claw mineralogy across four porcelain crab species from different habitats

Elevated concentration of carbon dioxide (elevated pCO2) that cause reduced pH is known to influence calcification in many marine taxa, but how elevated pCO2 influences cation composition of mineralized structures is less well studied. To a large extent, the degree to which elevated pCO2 impacts mineralized structures is influenced by physiological adaptation of organisms to environments where low pH is routinely experienced. Here, we test the hypotheses that elevated pCO2 will differently impact the relative concentrations of divalent cations (Ca2+, Mg2+, Sr2+, and Mn2+) in four closely related species of porcelain crabs distributed across intertidal zone gradients. Cation composition of carapace and claw exoskeleton was determined using inductively coupled plasma mass spectrometry following 24-day exposures to pH/pCO2 levels of 8.0/418 and 7.4/1850 µatm during the intermoult period. Reduced pH/elevated pCO2 caused a 13–24% decrease of carapace [Ca2+] across all species, and species-specific responses in carapace and claw [Mg2+], [Sr2+] and [Mn2+] were observed. During a 24-day exposure, reduced pH/elevated pCO2 reduced survival probability in low-intertidal but not mid-intertidal species. Overall, the effect of reduced pH/elevated pCO2 on exoskeleton mineral composition was muted in mid-intertidal species relative to low-intertidal species, indicating that extant adaptation to the variable intertidal zone may lessen the impact of ocean acidification (OA) on maintenance of mineralized structures. Differences in responses to reduced pH/elevated pCO2among closely related species adds complexity to predictive inferences regarding the effects of OA.

Continue reading ‘Effects of elevated pCO2 on crab survival and exoskeleton composition depend on shell function and species distribution: a comparative analysis of carapace and claw mineralogy across four porcelain crab species from different habitats’


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Ocean acidification in the IPCC AR5 WG II

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