Posts Tagged 'reproduction'

Trade-offs in a high CO2 habitat on a subsea volcano: condition and reproductive features of a bathymodioline mussel

Northwest Eifuku submarine volcano (Mariana Volcanic Arc) emits very high concentrations of CO2 at a vent where the mussel Bathymodiolus septemdierum experiences pH as low as 5.2. We examined how this natural setting of high pCO2 influences shell, body, and reproductive condition. Calcification is highly compromised: at a given shell volume, shells from NW Eifuku weigh about half those from reference sites in the south Pacific, and dissolution of the inner shell is evident. However, the condition indices of some NW Eifuku mussels were equal to or higher than those from Lau back-arc basin and the New Hebrides Island Arc. NW Eifuku mussels in pH 5.2 fluids had the highest symbiont abundances in gill bacteriocytes, probably due to greater dissolved sulphide access. Excess energy demands imposed by high pCO2 conditions appears moderated by adequate food availability through symbiont chemosynthesis. In the sample with the lowest body condition, gametogenesis was lagging, although all mussels in high pCO2 had developing gonads and the complete gametogenic cycle was present in our samples. Gamete development is synchronous between sexes and is possibly periodic. While mussels are functionally dioecious, protogynous hermaphroditism can occur—a first record for the genus—which may be an adaptation to resource availability. B. septemdierum likely makes energy allocation trade-offs among calcification, body mass maintenance, reproduction and other processes to maximize fitness. We suggest that flexibility to divert energy from shell formation, combined with good food supply, can mitigate the manifestation of high CO2 stress on B. septemdierum.

Continue reading ‘Trade-offs in a high CO2 habitat on a subsea volcano: condition and reproductive features of a bathymodioline mussel’

Potential impact of carbonate chemistry change (pCO2) on krill and krill-based food chain in the Southern Ocean with emphasis on embryogenesis of Antarctic krill

In the Southern Ocean, it is still not certain that overall krill biomass may decline because of drastic increase in pCO2, and consequent decline in pH. However, there is evidence that ecological vacuums created by krill population collapses caused by ecosystem shifts in Western Antarctic Peninsula (WAP) region led to replacement of Antarctic krill Euphausia superba by soft-bodied salps Salpa thomsoni. There is yet another questionable hypothesis that by the end of 21st century, ocean acidification stress, coupled with thermal increase, may synergistically induce physiologically critical stress to Antarctic krill in some areas of the Southern Ocean, egg development of krill may drastically decrease and in the 23rd century krill may even become extinct. I have earlier reported on normal krill egg development in relation to thermal change and high pressure (George and Stromberg, 1985). Recent experiments on krill development under different pCO2 conditions by Kawaguchi et al. (2011, 2013) suggest that we may witness 20 to 70 % reduction in Antarctic Krill by 2100 as direct consequence of pH decline. Such a scenario may lead to demise of krill-eating top-predators like baleen whales, seals and different species of Antarctic penguin populations. We now know that Adelaide penguins are decreasing in Bransfield Strait region off of the Western Antarctic Peninsula but increasing in Ross Sea region. Such a shift in breeding colonies moving from northern to southern WAP region and Ross Sea areas is not attributed to any decline in krill biomass but recent decadal melting of sea-ice as documented by remote sensing (George and Hayden, 2017). In this paper the main focus revolves around implications of changing chemistry of the Southern Ocean caused by absorption of anthropogenic carbon dioxide.
Continue reading ‘Potential impact of carbonate chemistry change (pCO2) on krill and krill-based food chain in the Southern Ocean with emphasis on embryogenesis of Antarctic krill’

Impacts of ocean acidification on sperm develop with exposure time for a polychaete with long lived sperm

The majority of marine invertebrate species release eggs and sperm into seawater for external fertilisation. Seawater conditions are currently changing at an unprecedented rate as a consequence of ocean acidification (OA). Sperm are thought to be particularly vulnerable to these changes and may be exposed to external environmental conditions for variable periods of time between spawning and fertilisation. Here, we undertook a mechanistic investigation of sperm swimming performance in the coastal polychaete Arenicola marina during an extended exposure to OA conditions (pHNBS 7.77, 1000 μatm pCO2). We found that key fitness-related aspects of sperm functioning declined faster under OA conditions i.e. impacts became apparent with exposure time. Sperm swimming speed (VCL), the number of motile sperm and sperm path linearity all dropped significantly after 4 h under OA conditions whilst remaining constant under ambient conditions at this time point. Our results highlight the importance of sperm exposure duration in ocean acidification experiments and may help towards explaining species specific differences in response.

Continue reading ‘Impacts of ocean acidification on sperm develop with exposure time for a polychaete with long lived sperm’

Physiological implications of ocean acidification for marine fish: emerging patterns and new insights

Ocean acidification (OA) is an impending environmental stress facing all marine life, and as such has been a topic of intense research interest in recent years. Numerous detrimental effects have been documented in marine fish, ranging from reduced mortality to neurosensory impairment, and the prevailing opinions state that these effects are largely the downstream consequences of altered blood carbon dioxide chemistry caused by respiratory acid–base disturbances. While the respiratory acid–base disturbances are consistent responses to OA across tested fish species, it is becoming increasingly clear that there is wide variability in the degree of downstream impairments between species. This can also be extended to intraspecies variability, whereby some individuals have tolerant physiological traits, while others succumb to the effects of OA. This review will synthesize relevant literature on marine fish to highlight consistent trends of impairment, as well as observed interspecies variability in the responses to OA, and the potential routes of physiological acclimation. In all cases, whole animal responses are linked to demonstrated or proposed physiological impairments. Major topics of focus include: (1) respiratory acid–base disturbances; (2) early life survival and growth; (3) the implications for metabolic performance, activity, and reproduction; and (4) emerging physiological theories pertaining to neurosensory impairment and the role of GABAA receptors. Particular emphasis is placed on the importance of understanding the underlying physiological traits that confer inter- and intraspecies tolerance, as the abundance of these traits will decide the long-term outlook of marine fish.

Continue reading ‘Physiological implications of ocean acidification for marine fish: emerging patterns and new insights’

Spatial patterns of Anchoveta (Engraulis ringens) eggs and larvae in relation to pCO2 in the Peruvian upwelling system

Large and productive fisheries occur in regions experiencing or projected to experience ocean acidification. Anchoveta (Engraulis ringens) constitute the world’s largest single-species fishery and live in one of the ocean’s highest pCO2 regions. We investigated the relationship of the distribution and abundance of Anchoveta eggs and larvae to natural gradients in pCO2 in the Peruvian upwelling system. Eggs and larvae, zooplankton, and data on temperature, salinity, chlorophyll a and pCO2 were collected during a cruise off Peru in 2013. pCO2 ranged from 167–1392 µatm and explained variability in egg presence, an index of spawning habitat. Zooplankton abundance explained variability in the abundance of small larvae. Within the main spawning and larva habitats (6–10°S), eggs were found in cool, low-salinity, and both extremely low (less than 200 µatm) and high (more than 900 µatm) pCO2 waters, and larvae were collected in warmer, higher salinity, and moderate (400–600 µatm) pCO2 waters. Our data support the hypothesis that Anchoveta preferentially spawned at high pCO2 and these eggs had lower survival. Enhanced understanding of the influence of pCO2 on Anchoveta spawning and larva mortality, together with pCO2 measurements, may enable predictions of ocean acidification effects on Anchoveta and inform adaptive fisheries management.

Continue reading ‘Spatial patterns of Anchoveta (Engraulis ringens) eggs and larvae in relation to pCO2 in the Peruvian upwelling system’

The combined effects of increased temperature and ocean acidification on the early life history stages of Caribbean coral and its implication for the recovery potential of Florida reefs

The early life history stages of coral are an essential component determining the recovery potential of coral reefs through sexual reproduction and recruitment. The pelagic larval phase is inherent in all coral species regardless of differing reproductive strategies and is the only time in coral life history where large scale movement is possible allowing for the repopulation of reef areas both within and outside the natal reef habitat. In the face of climate change, the larval dispersal and recruitment phase will take place in a warmer more acidic ocean if we continue on the path of unabated fossil fuel emissions. While much research has focused on how increased temperature or ocean acidification affect coral larvae independently, our understanding of how these factors interact to shape larval response is limited, especially in regards to Caribbean coral species.

To gain a better understanding of how the early life history stages of Caribbean coral may be affected by climate change, this dissertation investigates the effects of increased temperature (2.5 °C above historical averages in the Florida Keys) and carbon dioxide levels (900-1000 parts per million CO2) on corals from the Florida Reef tract by investigating the effects on larval metabolism, survivorship, settlement, and post-settlement growth and survival. Additionally, a coupled biophysical model was developed to determine the potential changes in connectivity that may result from the biological effects of increased temperature and ocean acidification on the larval phase. The larval respiratory response of three Caribbean coral species revealed Orbicella faveolata as the most environmentally responsive with significant increases in respiration after 1 day exposure to increased temperature (68% greater than control conditions) with a counteracting effect of ocean acidification significantly decreasing respiration. The changes in metabolism over time correlated with decreased time to competency under elevated temperature in O. faveolata larvae, resulting in a greater number of settlers (76% greater than control) and a relative increase in local retention and self-recruitment rates as revealed by the biophysical model (5 and 7% greater than control respectively). However, when increased temperature occurred in combination with elevated CO2 levels, respiration was not significantly increased relative to control conditions and development of competency is minimally impacted. This resulted in a smaller increase in settlers (13% greater than control) and no significant changes in connectivity patterns. The post-settlement phase was similarly impacted with counteracting effects of increased temperature and ocean acidification on recruit growth.

Overall, this dissertation reveals the potential for adaptation to increased temperature in at least one important coral species (Orbicella faveolata) that is greatly diminished when encountered in combination with ocean acidification. These results encourage the reduction of carbon emissions to give coral species the chance to adapt to elevated temperatures through the recruitment of more resilient individuals without the additional stress of ocean acidification.

Continue reading ‘The combined effects of increased temperature and ocean acidification on the early life history stages of Caribbean coral and its implication for the recovery potential of Florida reefs’

Effects of current and future coastal upwelling conditions on the fertilization success of the red abalone (Haliotis rufescens)

Acidification, deoxygenation, and warming are escalating changes in coastal waters throughout the world ocean, with potentially severe consequences for marine life and ocean-based economies. To examine the influence of these oceanographic changes on a key biological process, we measured the effects of current and expected future conditions in the California Current Large Marine Ecosystem on the fertilization success of the red abalone (Haliotis rufescens). Laboratory experiments were used to assess abalone fertilization success during simultaneous exposure to various levels of seawater pH (gradient from 7.95 to 7.2), dissolved oxygen (DO) ($60 and 180 mm. kg SW) and temperature (9, 13, and 18 C). Fertilization success declined continuously with decreasing pH but dropped precipitously below a threshold near pH 7.55 in cool (9 C—upwelling) to average (13 C) seawater temperatures. Variation in DO had a negligible effect on fertilization. In contrast, warmer waters (18 C) often associated with El Nino Southern Oscillation conditions in central California acted antagonistically with decreasing pH, largely reducing the strong negative influence below the pH threshold. Experimental approaches that examine the interactive effects of multiple environmental drivers and also strive to characterize the functional response of organisms along gradients in environmental change are becoming increasingly important in advancing our understanding of the real-world consequences of changing ocean conditions.

Continue reading ‘Effects of current and future coastal upwelling conditions on the fertilization success of the red abalone (Haliotis rufescens)’


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