Seawater carbonate chemistry and biological processes of bivalve shellfish Mercenaria mercenaria and Argopecten irradians during experiments, 2011

The combustion of fossil fuels has enriched levels of CO2 in the world's oceans and decreased ocean pH. Although the continuation of these processes may alter the growth, survival, and diversity of marine organisms that synthesize CaCO3shells, the effects of ocean acidification since the dawn of the industrial revolution are not clear. Here we present experiments that examined the effects of the ocean's past, present, and future (21st and 22nd centuries) CO2concentrations on the growth, survival, and condition of larvae of two species of commercially and ecologically valuable bivalve shellfish (Mercenaria mercenariaand Argopecten irradians). Larvae grown under near preindustrial CO2concentrations (250 ppm) displayed significantly faster growth and metamorphosis as well as higher survival and lipid accumulation rates compared with individuals reared under modern day CO2 levels. Bivalves grown under near preindustrial CO2 levels displayed thicker, more robust shells than individuals grown at present CO2 concentrations, whereas bivalves exposed to CO2 levels expected later this century had shells that were malformed and eroded. These results suggest that the ocean acidification that has occurred during the past two centuries may be inhibiting the development and survival of larval shellfish and contributing to global declines of some bivalve populations.

Seawater carbonate chemistry and survival of mollusks: Mercenaria mercenaria, Argopecten irradians, and Crassostrea virginica during experiments, 2009

We present experiments that examined the metamorphosis, growth, and survivorship of larvae from three species of commercially and ecologically valuable shellfish (Mercenaria mercenaria, Argopecten irradians, and Crassostrea virginica) at the levels of CO2 projected to occur during the 21st century and beyond. Under CO2 concentrations estimated to occur later this century (~66 Pa, 650 ppm), M. mercenaria and A. irradians larvae exhibited dramatic declines (>50%) in survivorship as well as significantly delayed metamorphosis and significantly smaller sizes. Although C. virginica larvae also experienced lowered growth and delayed metamorphosis at ~66 Pa CO2, their survival was only diminished at ~152 Pa CO2. The extreme sensitivity of larval stages of shellfish to enhanced levels of CO2 indicates that current and future increases in pelagic CO2 concentrations may deplete or alter the composition of shellfish populations in coastal ecosystems.

Seawater carbonate chemistry, calcification and shell size of hard clam Mercenaria mercenaria during experiments, 2011

Increasing atmospheric carbon dioxide threatens to decrease pH in the world's oceans. Coastal and estuarine calcifying organisms of significant ecological and economical importance are at risk; however, several biogeochemical processes drive pH in these habitats. In particular, coastal and estuarine sediments are frequently undersaturated with respect to calcium carbonate due to high rates of organic matter remineralization, even when overlying waters are saturated. As a result, the post-larval stages of infaunal marine bivalves must be able to deposit new shell material in conditions that are corrosive to shell. We measured calcification rates on the hard clam, Mercenaria spp.,in 5 post-larval size classes (0.39, 0.56, 0.78, 0.98, and 2.90 mm shell height) using the alkalinity anomaly method. Acidity of experimental water was controlled by bubbling with air-CO2 blends to obtain pH values of 8.02, 7.64, and 7.41, corresponding to pCO2 values of 424, 1120, and 1950 µatm. These pH values are typical of those found in many near-shore terrigenous marine sediments. Our results show that calcification rate decreased with lower pH in all 5 size classes measured. We also found a significant effect of size on calcification rate, with the smaller post-larval sizes unable to overcome dissolution pressure. Increased calcification rate with size allowed the larger sizes to overcome dissolution pressure and deposit new shell material under corrosive conditions. Size dependency of pH effects on calcification is likely due to organogenesis and developmental shifts in shell mineralogy occurring through the post-larval stage. Furthermore, we found significantly different calcification rates between the 2 sources of hard clams we used for these experiments, most likely due to genotypic differences. Our findings confirm the susceptibility of the early life stages of this important bivalve to decreasing pH and reveal mechanisms behind the increased mortality in post-larval juvenile hard clams related to dissolution pressure, that has been found in previous studies.

Detection histories for eight species of Amazona parrots in Venezuela during the NeoMaps bird surveys in 2010

Documenting changes in distribution is necessary for understanding species' response to environmental changes, but data on species distributions are heterogeneous in accuracy and resolution. Combining different data sources and methodological approaches can fill gaps in knowledge about the dynamic processes driving changes in species-rich, but data-poor regions. We combined recent bird survey data from the Neotropical Biodiversity Mapping Initiative (NeoMaps) with historical distribution records to estimate potential changes in the distribution of eight species of Amazon parrots in Venezuela. Using environmental covariates and presence-only data from museum collections and the literature, we first used maximum likelihood to fit a species distribution model (SDM) estimating a historical maximum probability of occurrence for each species. We then used recent, NeoMaps survey data to build single-season occupancy models (OM) with the same environmental covariates, as well as with time- and effort-dependent detectability, resulting in estimates of the current probability of occurrence. We finally calculated the disagreement between predictions as a matrix of probability of change in the state of occurrence. Our results suggested negative changes for the only restricted, threatened species, Amazona barbadensis, which has been independently confirmed with field studies. Two of the three remaining widespread species that were detected, Amazona amazonica, Amazona ochrocephala, also had a high probability of negative changes in northern Venezuela, but results were not conclusive for Amazona farinosa. The four remaining species were undetected in recent field surveys; three of these were most probably absent from the survey locations (Amazona autumnalis, Amazona mercenaria and Amazona festiva), while a fourth (Amazona dufresniana) requires more intensive targeted sampling to estimate its current status. Our approach is unique in taking full advantage of available, but limited data, and in detecting a high probability of change even for rare and patchily-distributed species. However, it is presently limited to species meeting the strong assumptions required for maximum-likelihood estimation with presence-only data, including very high detectability and representative sampling of its historical distribution.

Data compilation on the biological response to ocean acidification: environmental and experimental context of data sets and related literature

The exponential growth of studies on the biological response to ocean acidification over the last few decades has generated a large amount of data. To facilitate data comparison, a data compilation hosted at the data publisher PANGAEA was initiated in 2008 and is updated on a regular basis (doi:10.1594/PANGAEA.149999). By January 2015, a total of 581 data sets (over 4 000 000 data points) from 539 papers had been archived. Here we present the developments of this data compilation five years since its first description by Nisumaa et al. (2010). Most of study sites from which data archived are still in the Northern Hemisphere and the number of archived data from studies from the Southern Hemisphere and polar oceans are still relatively low. Data from 60 studies that investigated the response of a mix of organisms or natural communities were all added after 2010, indicating a welcomed shift from the study of individual organisms to communities and ecosystems. The initial imbalance of considerably more data archived on calcification and primary production than on other processes has improved. There is also a clear tendency towards more data archived from multifactorial studies after 2010. For easier and more effective access to ocean acidification data, the ocean acidification community is strongly encouraged to contribute to the data archiving effort, and help develop standard vocabularies describing the variables and define best practices for archiving ocean acidification data.