Posts Tagged 'crustaceans'



Behavioral defenses of shellfish prey under ocean acidification

Biological interactions between predators and prey constitute a key component of the ecology and evolution of marine systems, and animal behavior can affect the outcome of predator–prey interactions. It has been recently demonstrated that CO2-induced ocean acidification can alter the behavior of marine organisms and potentially alter predator–prey dynamics. This study combines both quantitative (meta-analysis) and qualitative approaches to review the effects of ocean acidification on behavioral prey defenses in marine invertebrates. A systematic literature search identified 34 studies that experimentally assessed behavioral defenses under elevated pCO2 spanning three phyla: crustaceans, echinoderms, and molluscs. A meta-analysis suggested that exposure to elevated seawater pCO2 can negatively affect behavioral defenses in bivalve molluscs and malacostracan crustaceans. By contrast, defenses of cephalopod molluscs seem to be positively impacted by elevated pCO2, whereas gastropods and echinoids appear unaffected. A qualitative assessment of studies on combined effects of ocean acidification and warming revealed that combined effects typically differ from ocean acidification–only effects. Based on a qualitative assessment of three studies to date, neurological interference of GABAA receptors under elevated pCO2 may play a major role in ocean acidification effects on prey defense behaviors; however, more research is needed, and other mechanistic underpinnings are also important to consider. Ultimately, the results of this study suggest that behavioral prey defenses in some shellfish taxa may be vulnerable to ocean acidification, that the effects of ocean acidification are often different under warming scenarios than under present-day temperature scenarios, and that GABAA interference may be an important mechanism underpinning behavioral responses of shellfish prey under ocean acidification. Despite the importance of shellfish behavioral defenses in the ecology and evolution of marine biological communities, however, research to date has only scraped the surface in understanding ocean acidification effects. Increased research efforts on the effects of multiple stressors, acclimation and adaptation, environmental variability, and complex situational and ecological contexts are needed. Studies of fish behavioral defenses under ocean acidification can help streamline hypotheses and experimental approaches, particularly given the similar effects of elevated pCO2 on GABAA function.

Continue reading ‘Behavioral defenses of shellfish prey under ocean acidification’

Effects of elevated CO2 on survival, growth, digestive enzymes and glucose concentration of white leg shrimp (Litopenaeus vannamei Boone, 1931) from postlarvae 15 to juvenile stage (in Vietnamese)

This study was carried out to determine the effects of CO2 on survival, growth, digestive enzyme activity and glucose concentration of white leg shrimp from 15-day postlarvae to juvenile stage. The study was designed using a completely randomized with 4-CO2 treatments including 2.32, 7.81, 19.0 and 45.6 mg/L equal to pH of 8.1, 7.6, 7.2 and 6.8, respectively. Postlarvae of 0.019 g and 1.20 cm length were stocked at the density of 100 ind./200-L tank. After 45 days, the survival rate of shrimp in control treatment (2.32 mg/L CO2 or pH=8.1) was 70.0%, and the lowest survival rate occurred in the CO2 treatment of 45.6 mg/L (28.3%). The lowest final individual weight and length in CO2 concentration of 45.6 mg/L were 1.09 g and 4.69 cm. The lowest enzyme activities were in CO2 treatment of 45.6 mg/L. Glucose concentration was highest in 37.5 mg/100 mL. The high CO2 concentration will adversely affect growth, survival rate, reduce some digestive enzymes and increase glucose concentration in hemolymph of white leg shrimp.

Continue reading ‘Effects of elevated CO2 on survival, growth, digestive enzymes and glucose concentration of white leg shrimp (Litopenaeus vannamei Boone, 1931) from postlarvae 15 to juvenile stage (in Vietnamese)’

Antagonistic interplay between pH and food resources affects copepod traits and performance in a year-round upwelling system

Linking pH/pCO2 natural variation to phenotypic traits and performance of foundational species provides essential information for assessing and predicting the impact of ocean acidification (OA) on marine ecosystems. Yet, evidence of such linkage for copepods, the most abundant metazoans in the oceans, remains scarce, particularly for naturally corrosive Eastern Boundary Upwelling systems (EBUs). This study assessed the relationship between pH levels and traits (body and egg size) and performance (ingestion rate (IR) and egg reproduction rate (EPR)) of the numerically dominant neritic copepod Acartia tonsa, in a year-round upwelling system of the northern (23° S) Humboldt EBUs. The study revealed decreases in chlorophyll (Chl) ingestion rate, egg production rate and egg size with decreasing pH as well as egg production efficiency, but the opposite for copepod body size. Further, ingestion rate increased hyperbolically with Chl, and saturated at ~1 µg Chl. L−1. Food resources categorized as high (H, >1 µg L−1) and low (L,  7.89) and future (>400 µatm pCO2, pH < 7.89) were used to compare our observations to values globally employed to experimentally test copepod sensitivity to OA. A comparison (PERMANOVA) test with Chl/pH (2*2) design showed that partially overlapping OA levels expected for the year 2100 in other ocean regions, low-pH conditions in this system negatively impacted traits and performance associated with copepod fitness. However, interacting antagonistically with pH, food resource (Chl) maintained copepod production in spite of low pH levels. Thus, the deleterious effects of ocean acidification are modulated by resource availability in this system.

Continue reading ‘Antagonistic interplay between pH and food resources affects copepod traits and performance in a year-round upwelling system’

Multispecies yield and profit when exploitation rates vary spatially including the impact on mortality of ocean acidification on North Pacific crab stocks

A multi-species size-structured population dynamics model that can account for spatial structure and technical interactions between commercial fisheries was developed and applied to the snow and southern Tanner crab fisheries in the eastern Bering Sea. The model was then used as the basis for forecasts to calculate reference points related to yield and profit under the effects of ocean acidification on snow and southern Tanner crab. Stochastic projections that account for variation about the stock-recruitment relationship were undertaken for a constant F35% harvest strategy, a strategy that sets effort to maximize profit ignoring the effects of environmental variability such as ocean acidification, and the Acceptable Biological Catch control rule, which includes a reduction in fishing mortality rate when stocks are below target levels. Single- and four-area models led to similar fits to abundance and catch data, and provide similar estimates of time-trajectories of mature male biomass. The model is used to compute Maximum Sustainable Yield (MSY) and an upper bound on Maximum Economic Yield (uMEY). The effort levels that achieve MSY and uMEY were sensitive to whether a spatial or non-spatial model was used to calculate reference points and hence how technical interactions among species were accounted for. Dynamic projections based on various management strategies indicated that adopting a uMEY target level of effort leads to some robustness to the effects of ocean acidification, although similar results can be obtained using the Acceptable Biological Catch control rule, which reduces harvest rates as biomass levels decline.

Continue reading ‘Multispecies yield and profit when exploitation rates vary spatially including the impact on mortality of ocean acidification on North Pacific crab stocks’

Resilience of oxygen consumption rates in the juvenile blue crab Callinectes sapidus to future predicted increases in environmental temperature and pCO2 in the Mesohaline Chesapeake Bay

Quantifying the physiological impact of environmental stressors on living organisms is critical to predicting the response of any given species to future climate scenarios. Oxygen consumption rates (μmol/g/min) were measured to examine the physiological response of the juvenile blue crab Callinectes sapidus from the Chesapeake Bay (Patuxent River, Maryland) to elevated temperature and dissolved carbon dioxide in water (pCO2) reflective of projected future climate scenarios. Treatment levels were selected to represent current conditions in the Chesapeake Bay (26°C and 800 μatm) and conditions predicted to occur by the year 2100 (31°C and 8,000 μatm). Crabs were exposed in a factorial design to these conditions throughout two successive molts (approximately 30 days). At the end of the exposure, the oxygen consumption rates of individual crabs were determined over at least a 10-h period using a flow-through respiration chamber equipped with optical oxygen electrodes. No significant effect of temperature or pCO2 on oxygen consumption was observed, suggesting the absence of a respiratory impact of these two climate stressors on juvenile blue crabs. Oxygen consumption rates were also determined for crabs that experienced a rapid increase in temperature without prior acclimation. The oxygen consumption rate of crabs may have acclimated to increased temperature during the 30-day exposure period before respiratory measurement. This potential acclimation, combined with high individual variability, and a relatively small difference in temperature treatments are likely the cause for the lack of a statistically significant difference in mean oxygen consumption rates by temperature in the core experiment. The results of this study suggest that the blue crab may be quite resilient to future climate stressors and underscore the need for species-specific studies to quantify the effects of climate change on estuarine crustaceans.

Continue reading ‘Resilience of oxygen consumption rates in the juvenile blue crab Callinectes sapidus to future predicted increases in environmental temperature and pCO2 in the Mesohaline Chesapeake Bay’

Effect of pH on survival, egg production and feeding of Pseudodiaptomusannandaleia key fish food organism-a laboratory study

Calanoid copepods are key components of the marine food web and the food sources of many larval fishes and planktivores, and grazers of phytoplankton. Understanding the ranges of major environmental variables suitable for their
growth is essential to maintain the balance between trophic links and resources protection. The effects of exposure to pH ranging from 4.2 to 9.2 on survival, egg production and feeding rate were determined for adult copepod Pseudodiaptomusannandalei. Survival was maximum at pH 8.2 (control) and the optimum pH ranged between 6.2 and 8.2. The overall feeding rate fluctuated between 208-650 cells/ ml. The egg production rate (EPR) varied from 0 – 44±3.22 eggs/female. It is inferred that exposure to lower pH caused a significant decrease in both survival and EPR. However, feeding rate was not affected considerably. Our experimental results prove that pH stress has considerable effect on survival and fecundity of P. annandalei. However, feeding rate stayed
stable in most of the pH tested.

Continue reading ‘Effect of pH on survival, egg production and feeding of Pseudodiaptomusannandaleia key fish food organism-a laboratory study’

Analysis of effects of environmental fluctuations on the marine mysid Neomysis awatschensis and its development as an experimental model animal

Highlights

• Investigation of optimized culture conditions in temperature, salinity, and pH for mysid mass-culture and development as a laboratory model

• Identification of strong correlations between growth parameter and 20E level in environmental fluctuations

• Measurement of maternal effects of environmental fluctuations on second generation

Abstract

Mysids are experimental models and are among the most important food items for animals in aquaria and that support fisheries, and even for humans, but information on their performance in controlled culture systems is still limited. We reared the marine mysid Neomysis awatschensis in a controlled laboratory system, and measured its growth, 20–hydroxyecdysone (20E) levels, molting, and survival in response to environmental fluctuations in temperature, pH, and salinity, and inferred their potential associations based on annual field sampling. The 20E levels were significantly elevated during the postnauplioid stages, and even higher levels of 20E were maintained in the adult stages than in the nauplioid stages. Values of growth parameters (i.e. total length and the lengths of the antennal scale, expod, endopod, and telson) and 20E levels were higher during a 40-day period at 25 °C than at other temperatures, with shorter intermolt intervals, although morality was also increased. Among the surviving mysids, the number of newly hatched juveniles produced was higher for females exposed to 20 °C than that in other groups. Relatively higher growth and survival rates were measured at salinities over 25 practical salinity, while lower salinities under 15 practical salinity significantly reduced growth and survival. The number of newly hatched juveniles was lower at salinities under 15 practical salinity compared to those over 20 practical salinity. Overall, low temperature and salinity reduced mysid reproduction and the maintenance of the second generation. In the case of pH variation (pH of 7.0–8.0), there were no significant effects on growth and the number of newly hatched juveniles, although the survival rate was slightly lower and the 20E level fluctuated at a pH of 7.0. We believe that these associations between growth and environmental conditions can provide crucial information for optimizing mass mysid culture for experimental and ecotoxicological usage in the laboratory.

Continue reading ‘Analysis of effects of environmental fluctuations on the marine mysid Neomysis awatschensis and its development as an experimental model animal’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book