Posts Tagged 'crustaceans'

Rapid bioerosion in a tropical upwelling coral reef

Coral reefs persist in an accretion-erosion balance, which is critical for understanding the natural variability of sediment production, reef accretion, and their effects on the carbonate budget. Bioerosion (i.e. biodegradation of substrate) and encrustation (i.e. calcified overgrowth on substrate) influence the carbonate budget and the ecological functions of coral reefs, by substrate formation/consolidation/erosion, food availability and nutrient cycling. This study investigates settlement succession and carbonate budget change by bioeroding and encrusting calcifying organisms on experimentally deployed coral substrates (skeletal fragments of Stylophora pistillata branches). The substrates were deployed in a marginal coral reef located in the Gulf of Papagayo (Costa Rica, Eastern Tropical Pacific) for four months during the northern winter upwelling period (December 2013 to March 2014), and consecutively sampled after each month. Due to the upwelling environmental conditions within the Eastern Tropical Pacific, this region serves as a natural laboratory to study ecological processes such as bioerosion, which may reflect climate change scenarios. Time-series analyses showed a rapid settlement of bioeroders, particularly of lithophagine bivalves of the genus Lithophaga/Leiosolenus (Dillwyn, 1817), within the first two months of exposure. The observed enhanced calcium carbonate loss of coral substrate (>30%) may influence seawater carbon chemistry. This is evident by measurements of an elevated seawater pH (>8.2) and aragonite saturation state (Ωarag >3) at Matapalo Reef during the upwelling period, when compared to a previous upwelling event observed at a nearby site in distance to a coral reef (Marina Papagayo). Due to the resulting local carbonate buffer effect of the seawater, an influx of atmospheric CO2 into reef waters was observed. Substrates showed no secondary cements in thin-section analyses, despite constant seawater carbonate oversaturation (Ωarag >2.8) during the field experiment. Micro Computerized Tomography (μCT) scans and microcast-embeddings of the substrates revealed that the carbonate loss was primarily due to internal macrobioerosion and an increase in microbioerosion. This study emphasizes the interconnected effects of upwelling and carbonate bioerosion on the reef carbonate budget and the ecological turnovers of carbonate producers in tropical coral reefs under environmental change.

Continue reading ‘Rapid bioerosion in a tropical upwelling coral reef’

Elevated pCO2 affects feeding behaviour and acute physiological response of the brown crab Cancer pagurus

Anthropogenic climate change exposes marine organisms to CO2 induced ocean acidification (OA). Marine animals may make physiological and behavioral adaptations to cope with OA. Elevated pCO2 may affect metabolism, feeding and energy partition of marine crabs, and thereby affect their predator-prey dynamics with mussels. Therefore, we examined the effects of simulated future elevated pCO2 on feeding behavior and energy metabolism of the brown crab Cancer pagurus. Following 54 days of pre-acclimation to control CO2 levels (360 μatm) at 11 °C, crabs were exposed to consecutively increased oceanic CO2 levels (two weeks for 1200 and 2300 μatm, respectively) and subsequently returned to control CO2 level (390 μatm) for two weeks in order to study their potential to acclimate elevated pCO2 and recovery performance. Standard metabolic rate (SMR), specific dynamic action (SDA) and feeding behaviour of the crabs were investigated during each experimental period. Compared to the initial control CO2 conditions, the SMRs of CO2 exposed crabs were not significantly increased, but increased significantly when the crabs were returned to normal CO2 levels. Conversely, SDA was significantly reduced under high CO2 and did not return to control levels during recovery. Under high CO2, crabs fed on smaller sized mussels than under control CO2; food consumption rates were reduced; foraging parameters such as searching time, time to break the prey, eating time and handling time were all significantly longer than under control CO2, and prey profitability was significantly lower than that under control conditions. Again, a two-week recovery period was not sufficient for feeding behavior to return to control values. PCA results revealed a positive relationship between feeding/SDA and pH, but negative relationships between the length of foraging periods and pH. In conclusion, elevated pCO2 caused crab metabolic rate to increase at the expense of SDA. Elevated pCO2 affected feeding performance negatively and prolonged foraging periods. These results are discussed in the context of how elevated pCO2 may impair the competitiveness of brown crabs in benthic communities.

Continue reading ‘Elevated pCO2 affects feeding behaviour and acute physiological response of the brown crab Cancer pagurus’

Hypercapnia-induced disruption of long-distance mate-detection and reduction of energy expenditure in a coastal keystone crustacean

• Long-distance mate tracking in males was disrupted by high CO2 exposure.
• High CO2-exposed males exhibited increased latency in response to female cues.
• Both males and females exhibited metabolic depression, likely as compensation.
• High CO2 potentially disrupts chemosensory-dependent behaviours in amphipods.

Ocean acidification (OA) has been shown to disrupt behavioural responses either by affecting metabolic processes, or by effectively impairing an organisms’ ability to gather and assess information and make decisions. Given the lack of information regarding the effects of high CO2 on olfactory-mediated mating behaviours in crustaceans, the possible chemosensory disruption in male mate-tracking in the keystone amphipod (Gammarus locusta) was assessed (after a two-generation acclimation to high CO2 conditions). In a series of behavioural trials, the response time, first direction of movement and the proportion of time spent in the presence of female scent cues were quantified. The possibility of high CO2-induced metabolic changes was assessed through routine metabolic rate (RMR) quantification. We found that hypercapnia was responsible for inducing a delay in response time latency and effectively disrupted accurate female cue-tracking. Moreover, RMR were significantly reduced under high CO2 in both genders. Such finding supports the hypothesis of hypercapnia-induced metabolic depression, which potentially underpins the increased latency in response time verified. Overall, the present study hints the potential disruption of chemosensory-dependent sexual behaviours, through some degree of chemosensory and metabolic disruption. These results emphasize the need for further behavioural tests regarding chemosensory communication in amphipods and energy metabolism, and suggest cascading consequences for the species’ reproductive success and overall fitness in a future less alkaline ocean.

Continue reading ‘Hypercapnia-induced disruption of long-distance mate-detection and reduction of energy expenditure in a coastal keystone crustacean’

A microcosm study on the impact of acidification on feeding, survival, nauplii production rate, post-embryonic development and nutritional composition of marine copepod

Ocean acidification is the ongoing decrease in the pH of the oceans, caused by their uptake of anthropogenic carbon dioxide from the atmosphere. Increased carbon dioxide (CO2) from the burning of fossil fuels and other human activities continues to affect our atmosphere, resulting in global warming and climate change. Less well known is that this carbon dioxide is altering the chemistry of the surface oceans and causing them to become more acidic. From scientists and marine resource managers to policy- and decision-makers, there is a growing concern that the process called ocean acidification could have significant consequences on marine organisms which may alter species composition, disrupt marine food webs and ecosystems and potentially damage fishing, tourism and other human activities connected to the seas.

Continue reading ‘A microcosm study on the impact of acidification on feeding, survival, nauplii production rate, post-embryonic development and nutritional composition of marine copepod’

Caprellid amphipods (Caprella spp.) are vulnerable to both physiological and habitat-mediated effects of ocean acidification

Ocean acidification (OA) is one of the most significant threats to marine life, and is predicted to drive important changes in marine communities. Although OA impacts will be the sum of direct effects mediated by alterations of physiological rates and indirect effects mediated by shifts in species interactions and biogenic habitat provision, direct and indirect effects are rarely considered together for any given species. Here, we assess the potential direct and indirect effects of OA on a ubiquitous group of crustaceans: caprellid amphipods (Caprella laeviuscula and Caprella mutica). Direct physiological effects were assessed by measuring caprellid heart rate in response to acidification in the laboratory. Indirect effects were explored by quantifying caprellid habitat dependence on the hydroid Obelia dichotoma, which has been shown to be less abundant under experimental acidification. We found that OA resulted in elevated caprellid heart rates, suggestive of increased metabolic demand. We also found a strong, positive association between caprellid population size and the availability of OA-vulnerable O. dichotoma, suggesting that future losses of biogenic habitat may be an important indirect effect of OA on caprellids. For species such as caprellid amphipods, which have strong associations with biogenic habitat, a consideration of only direct or indirect effects could potentially misestimate the full impact of ocean acidification.

Continue reading ‘Caprellid amphipods (Caprella spp.) are vulnerable to both physiological and habitat-mediated effects of ocean acidification’

Analysis of Na+/K+ -ATPase gene expression and physiological parameters in the crab Callinectes danae submitted to future scenarios of ocean acidification in the laboratory (in Portuguese)

Oceanic acidification, a process resulting from the emission of carbon dioxide (CO2) in the atmosphere by activities of anthropic nature, has been causing in recent decades a change in the chemical balance of the bicarbonate / carbonate system and consequently a decrease in the pH of the oceans. Estimates indicate that this decrease can be 0.7 units per year of 2300, which can affect the growth, reproduction and even survival of the species. In this sense, studies are needed to evaluate the impact of oceanic acidification on physiological and molecular levels in different marine species. The Callinectes danae crab is an important ecological and economic resource of the Region of the Baixada Santista and inhabitant of different ranges of salinity. The present study evaluated the effects of ocean acidification on C. danae crab on a set of physiological parameters (oxygen consumption, ammonia excretion, O: N ratio, hepatosomatic index and osmo-and ionoregulatory capacity of hemolymph), and gene expression of Na + / K + – ATPase, an important enzyme in the process of osmoregulation and acid base balance. The animals were kept at different salinities (20, 25, 30, 35 and 40) and at pHs 8.0 (control) and 7.3 (acidified) for a period of three and thirty days. It was observed an increase in the oxygen consumption in salinities 25 (3 days), 20 and 40 (30 days) probably due to a greater energy requirement for the maintenance of systems related to acid-base regulation. Metabolic depression was also observed at the salinity of 30 (30 days). Ammonia excretion decreased in salinities 30 (3 days), 25, 30 and 35 (30 days) possibly due to competition between Na + / H + and Na + / NH + 4 transporters. The hepatosomatic index had an increase in salinities of 30 (3 days) and 40 (30 days) due to a possible accumulation of reserves in stressful situations. The energy substrate and the osmoregulatory pattern remained unchanged in all treatments. However, the Cl- and Na + concentrations were reduced at the salinity of 25 and 35 (30 days), probably due to some changes in their transporters. Molecularly, a regulation of Na + / K + ATPase expression was observed, with a decrease in salinities of 35 and 40 (3 days), and a subsequent increase in the period of 30 days. The work was the first to evaluate the physiological and molecular parameters of C.danae in different salinities. Animals that remained longer on exposure to high pCO2 are more negatively affected than animals that were exposed in 3 days. The observed changes may indicate that although C. danae is an eurialan animal and inhabits different environments, ocean acidification can alter its physiological and molecular patterns, taking organisms out of their homeostasis, having consequences on the growth, development and distribution of the species.

Continue reading ‘Analysis of Na+/K+ -ATPase gene expression and physiological parameters in the crab Callinectes danae submitted to future scenarios of ocean acidification in the laboratory (in Portuguese)’

Ocean acidification drives community shifts towards simplified non-calcified habitats in a subtropical−temperate transition zone

Rising atmospheric concentrations of carbon dioxide are causing surface seawater pH and carbonate ion concentrations to fall in a process known as ocean acidification. To assess the likely ecological effects of ocean acidification we compared intertidal and subtidal marine communities at increasing levels of pCO2 at recently discovered volcanic seeps off the Pacific coast of Japan (34° N). This study region is of particular interest for ocean acidification research as it has naturally low levels of surface seawater pCO2 (280–320 µatm) and is located at a transition zone between temperate and sub-tropical communities. We provide the first assessment of ocean acidification effects at a biogeographic boundary. Marine communities exposed to mean levels of pCO2 predicted by 2050 experienced periods of low aragonite saturation and high dissolved inorganic carbon. These two factors combined to cause marked community shifts and a major decline in biodiversity, including the loss of key habitat-forming species, with even more extreme community changes expected by 2100. Our results provide empirical evidence that near-future levels of pCO2 shift sub-tropical ecosystems from carbonate to fleshy algal dominated systems, accompanied by biodiversity loss and major simplification of the ecosystem.

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Ocean acidification in the IPCC AR5 WG II

OUP book