A cold limit to adaptation in the sea

Temperature affects biological functions by altering reaction rates. Physiological rates usually double to treble for every 10°C rise, and 1–4 fold encompasses normal biological functions. However, in polar marine species inhabiting temperatures around 0°C many processes are slowed beyond the Arrhenius relationships for warmer water species. Growth, embryonic development, Specific dynamic action (SDA) duration, and time to acclimate to altered temperature, are all 5–12 fold slower in species living near 0°C than at 10°C. This cold marine physiological transition to slower states is absent, however, in oxygen consumption and SDA factorial scope; processes where capacity is related to aerobic scope. My opinion is that processes involving significant protein modification are impacted, and protein synthesis or folding problems cause the slowing of rates beyond expected temperature effects

Lack of an HSP70 heat shock response in two Antarctic marine invertebrates

Members of the HSP70 gene family comprising the inducible (HSP70) genes and GRP78 (glucose-regulated protein 78 kDa) were identified in an Antarctic sea star (Odontaster validus) and an Antarctic gammarid (Paraceradocus gibber). These genes were surveyed for expression levels via Q-PCR after an acute 2-hour heat shock experiment in both animals and a time course assay in O. validus. No significant up-regulation was detected for any of the genes in either of the animals during the acute heat shock. The time course experiment in O. validus produced slightly different results with an initial down regulation in these genes at 2°C, but no significant up-regulation of the genes either at 2 or 6°C. Therefore, the classical heat shock response is absent in both species. The data is discussed in the context of the organisms’ thermal tolerance and the applicability of HSP70 to monitor thermal stress in Antarctic marine organisms

Chapter 3 Antarctic Marine Biodiversity

Animals living in the Southern Ocean have evolved in a singular environment. It shares many of its attributes with the high Arctic, namely low, stable temperatures, the pervading effect of ice in its many forms and extreme seasonality of light and phytobiont productivity. Antarctica is, however, the most isolated continent on Earth and is the only one that lacks a continental shelf connection with another continent. This isolation, along with the many millions of years that these conditions have existed, has produced a fauna that is both diverse, with around 17,000 marine invertebrate species living there, and has the highest proportions of endemic species of any continent. The reasons for this are discussed. The isolation, history and unusual environmental conditions have resulted in the fauna producing a range and scale of adaptations to low temperature and seasonality that are unique. The best known such adaptations include channichthyid icefish that lack haemoglobin and transport oxygen around their bodies only in solution, or the absence, in some species, of what was only 20 years ago termed the universal heat shock response

Turning on the heat: ecological response to simulated warming in the sea

Significant warming has been observed in every ocean, yet our ability to predict the consequences of oceanic warming on marine biodiversity remains poor. Experiments have been severely limited because, until now, it has not been possible to manipulate seawater temperature in a consistent manner across a range of marine habitats. We constructed a "hot-plate'' system to directly examine ecological responses to elevated seawater temperature in a subtidal marine system. The substratum available for colonisation and overlying seawater boundary layer were warmed for 36 days, which resulted in greater biomass of marine organisms and a doubling of space coverage by a dominant colonial ascidian. The "hot-plate'' system will facilitate complex manipulations of temperature and multiple stressors in the field to provide valuable information on the response of individuals, populations and communities to environmental change in any aquatic habitat

Multiyear trend in reproduction underpins interannual variation in gametogenic development of an Antarctic urchin.

Ecosystems and their biota operate on cyclic rhythms, often entrained by predictable, small-scale changes in their natural environment. Recording and understanding these rhythms can detangle the effect of human induced shifts in the climate state from natural fluctuations. In this study, we assess long-term patterns of reproductive investment in the Antarctic sea urchin, Sterechinus neumayeri, in relation to changes in the environment to identify drivers of reproductive processes. Polar marine biota are sensitive to small changes in their environment and so serve as a barometer whose responses likely mirror effects that will be seen on a wider global scale in future climate change scenarios. Our results indicate that seasonal reproductive periodicity in the urchin is underpinned by a multiyear trend in reproductive investment beyond and in addition to, the previously reported 18–24 month gametogenic cycle. Our model provides evidence that annual reproductive investment could be regulated by an endogenous rhythm since environmental factors only accounted for a small proportion of the residual variation in gonad index. This research highlights a need for multiyear datasets and the combination of biological time series data with large-scale climate metrics that encapsulate multi-factorial climate state shifts, rather than using single explanatory variables to inform changes in biological processes

Latitudinal trends in shell production cost from the tropics to the poles

The proportion of body mass devoted to skeleton in marine invertebrates decreases along latitudinal gradients from large proportions in the tropics to small proportions in polar regions. A historical hypothesis—that latitudinal differences in shell production costs explain these trends—remains untested. Using field-collected specimens spanning a 79°N to 68°S latitudinal gradient (16,300 km), we conducted a taxonomically controlled evaluation of energetic costs of shell production as a proportion of the total energy budget in mollusks. Shell production cost was fairly low across latitudes at <10% of the energy budget and predominately <5% in gastropods and <4% in bivalves. Throughout life, shell cost tended to be lower in tropical species and increased slightly toward the poles. However, shell cost also varied with life stage, with the greatest costs found in young tropical gastropods. Low shell production costs on the energy budget suggest that shell cost may play only a small role in influencing proportional skeleton size gradients across latitudes relative to other ecological factors, such as predation in present-day oceans. However, any increase in the cost of calcium carbonate (CaCO3) deposition, including from ocean acidification, may lead to a projected ~50 to 70% increase in the proportion of the total energy budget required for shell production for a doubling of the CaCO3 deposition cost. Changes in energy budget allocation to shell cost would likely alter ecological trade-offs between calcification and other drivers, such as predation, in marine ecosystems

Ocean acidification does not impact shell growth or repair of the Antarctic brachiopod Liothyrella uva (Broderip, 1833)

Marine calcifiers are amongst the most vulnerable organisms to ocean acidification due to reduction in the availability of carbonate ions for skeletal/shell deposition. However, there are limited long-term studies on the possible impacts of increased pCO2 on these taxa. A 7 month CO2 perturbation experiment was performed on one of the most calcium carbonate dependent species, the Antarctic brachiopod Liothyrella uva, which inhabits the Southern Ocean where carbonate ion saturation levels are amongst the lowest on Earth. The effects of the predicted environmental conditions in 2050 and 2100 on the growth rate and ability to repair shell in L.uva were tested with four treatments; a low temperature control (0°C, pH7.98), a pH control (2°C, pH8.05), mid-century scenario (2°C, pH7.75) and end-century scenario (2°C, pH7.54). Environmental change impacts on shell repair are rarely studied, but here repair was not affected by either acidified conditions or temperature. Growth rate was also not impacted by low pH. Elevated temperature did, however, increase growth rates. The ability of L.uva to continue, and even increase shell production in warmer and acidified seawater suggests that this species can acclimate to these combined stressors and generate suitable conditions for shell growth at the site of calcification.Emma Cross is supported by the NERC PhD Studentship (NE/T/A/2011).This is the accepted manuscript. The final version is available at http://www.sciencedirect.com/science/article/pii/S0022098114002743

Ship traffic connects Antarctica's fragile coasts to worldwide ecosystems.

Antarctica, an isolated and long considered pristine wilderness, is becoming increasingly exposed to the negative effects of ship-borne human activity, and especially the introduction of invasive species. Here, we provide a comprehensive quantitative analysis of ship movements into Antarctic waters and a spatially explicit assessment of introduction risk for nonnative marine species in all Antarctic waters. We show that vessels traverse Antarctica's isolating natural barriers, connecting it directly via an extensive network of ship activity to all global regions, especially South Atlantic and European ports. Ship visits are more than seven times higher to the Antarctic Peninsula (especially east of Anvers Island) and the South Shetland Islands than elsewhere around Antarctica, together accounting for 88% of visits to Southern Ocean ecoregions. Contrary to expectations, we show that while the five recognized "Antarctic Gateway cities" are important last ports of call, especially for research and tourism vessels, an additional 53 ports had vessels directly departing to Antarctica from 2014 to 2018. We identify ports outside Antarctica where biosecurity interventions could be most effectively implemented and the most vulnerable Antarctic locations where monitoring programs for high-risk invaders should be established

Thicker Shells Compensate Extensive Dissolution in Brachiopods under Future Ocean Acidification.

Organisms with long generation times require phenotypic plasticity to survive in changing environments until genetic adaptation can be achieved. Marine calcifiers are particularly vulnerable to ocean acidification due to dissolution and a reduction in shell-building carbonate ions. Long-term experiments assess organisms' abilities to acclimatize or even adapt to environmental change. Here we present an unexpected compensatory response to extensive shell dissolution in a highly calcium-carbonate-dependent organism after long-term culture in predicted end-century acidification and warming conditions. Substantial shell dissolution with decreasing pH posed a threat to both a polar ( Liothyrella uva) and a temperate ( Calloria inconspicua) brachiopod after 7 months and 3 months exposure, respectively, with more extensive dissolution in the polar species. This impact was reflected in decreased outer primary layer thickness in the polar brachiopod. A compensatory response of increasing inner secondary layer thickness, and thereby producing a thicker shell, was exhibited by the polar species. Less extensive dissolution in the temperate brachiopod did not affect shell thickness. Increased temperature did not impact shell dissolution or thickness. Brachiopod ability to produce a thicker shell when extensive shell dissolution occurs suggests this marine calcifier has great plasticity in calcification providing insights into how similar species might cope under future environmental change

A 120-year record of resilience to environmental change in brachiopods

The inability of organisms to cope in changing environments poses a major threat to their survival. Rising carbon dioxide concentrations, recently exceeding 400 μatm, are rapidly warming and acidifying our oceans. Current understanding of organism responses to this environmental phenomenon is based mainly on relatively short‐ to medium‐term laboratory and field experiments, which cannot evaluate the potential for long‐term acclimation and adaptation, the processes identified as most important to confer resistance. Here, we present data from a novel approach that assesses responses over a centennial timescale showing remarkable resilience to change in a species predicted to be vulnerable. Utilising museum collections allows the assessment of how organisms have coped with past environmental change. It also provides a historical reference for future climate change responses. We evaluated a unique specimen collection of a single species of brachiopod (Calloria inconspicua) collected every decade from 1900 to 2014 from one sampling site. The majority of brachiopod shell characteristics remained unchanged over the past century. One response, however, appears to reinforce their shell by constructing narrower punctae (shell perforations) and laying down more shell. This study indicates one of the most calcium‐carbonate‐dependent species globally to be highly resilient to environmental change over the last 120 years and provides a new insight for how similar species might react and possibly adapt to future change