Understanding the margin squeeze: differentiation in fitness-related traits between central and trailing edge populations of Corallina officinalis

Assessing population responses to climate-related environmental change is key to understanding the adaptive potential of the species as a whole. Coralline algae are critical components of marine shallow water ecosystems where they function as important ecosystem engineers. Populations of the calcifying algae Corallina officinalis from the center (southern UK) and periphery (northern Spain) of the North Atlantic species natural distribution were selected to test for functional differentiation in thermal stress response. Physiological measurements of calcification, photosynthesis, respiration, growth rates, oxygen, and calcification evolution curves were performed using closed cell respirometry methods. Species identity was genetically confirmed via DNA barcoding. Through a common garden approach, we identified distinct vulnerability to thermal stress of central and peripheral populations. Southern populations showed a decrease in photosynthetic rate under environmental conditions of central locations, and central populations showed a decline in calcification rates under southern conditions. This shows that the two processes of calcification and photosynthesis are not as tightly coupled as previously assumed. How the species as whole will react to future climatic changes will be determined by the interplay of local environmental conditions and these distinct population adaptive traits.South African Research Chairs Initiative (SARChI) IF/01413/2014/CP1217/CT0004 University of Portsmouthinfo:eu-repo/semantics/publishedVersio

Structural and elemental analysis of the freshwater, low-Mg calcite coralline alga <i>pneophyllum cetinaensis</i>

Coralline algae are one of the most diversified groups of red algae and represent a major component of marine benthic habitats from the poles to the tropics. This group was believed to be exclusively marine until 2016, when the first freshwater coralline algae Pneophyllum cetinaensis was discovered in the Cetina River, southern Croatia. While several studies investigated the element compositions of marine coralline algal thalli, no information is yet available for the freshwater species. Using XRD, LA-ICP-MS and nano indentation, this study presents the first living low-Mg calcite coralline algae with Mg concentrations ten times lower than is common for the average marine species. Despite the lower Mg concentrations, hardness and elastic modulus (1.71 ± 1.58 GPa and 29.7 ± 18.0 GPa, respectively) are in the same range as other marine coralline algae, possibly due to other biogenic impurities. When compared to marine species, Ba/Ca values were unusually low, even though Ba concentrations are generally higher in rivers than in seawater. These low values might be linked to different physical and chemical characteristics of the Cetina River

Physiological response of the coralline alga Corallina officinalis L. to both predicted long-term increases in temperature and short-term heatwave events

This work was supported by the European Cooperation in Science and Technology (COST) within the COST Action CA15121, advancing marine conservation in the European and contiguous seas (MarCons).Climate change is leading to an increase of mean sea surface temperatures and extreme heat events. There is an urgent need to better understand the capabilities of marine macroalgae to adapt to these rapid changes. In this study, the responses of photosynthesis, respiration, and calcification to elevated temperature in a global warming scenario were investigated in the coralline alga Corallina officinalis. Algae were cultured for 7 weeks under 4 temperature treatments: (1) control under ambient-summer conditions (C, ∼20 °C), (2) simulating a one-week heatwave of 1 °C (HW, Tcontrol+1 °C), (3) elevated temperature (+3, Tcontrol +3 °C), (4) combination of the two previous treatments (HW+3, T+3+1 °C). After exposure at T+3 (up to a Tmax of ∼23 °C), respiration and photosynthesis increased significantly. After 5 weeks, calcification rates were higher at elevated temperatures (T+3 and THW+3) compared to Tcontrol, but at the end of the experiment (7 weeks) calcification decreased significantly at those temperatures beyond the thermal optimum (six-fold at T+3, and three-fold at THW+3, respectively). The same trend was noted for all the physiological processes, suggesting that a prolonged exposure to high temperatures (7 weeks up to T+3) negatively affect the physiology of C. officinalis, as a possible consequence of thermal stress. A one-week heatwave of +1 °C with respect to Tcontrol (at THW) did not affect respiration, photosynthesis, or calcification rates. Conversely, a heatwave of 1 °C, when combined with the 3 °C increase predicted by the end of the century (at THW+3), induced a reduction of physiological rates. Continued increases in both the intensity and frequency of heatwaves under anthropogenic climate change may lead to reduced growth and survival of primary producers such as C. officinalis.PostprintPeer reviewe

Seawater carbonate chemistry and primary production, respiration, calcification and growth rates of 6 populations of coralline alga Corallina officinalis

Rising levels of anthropogenic carbon dioxide (CO2) in the atmosphere over the past several decades has resulted in a changing climate and is projected to further fuel global climate change in future centuries. Key components of climate change in the ocean are ocean acidification (decreasing pH and carbonate ion concentration [ CO32- ]) and rising sea surface temperatures. While several studies have investigated the effect of these climatic changes on a single population, very few studies have addressed effects on populations living at the margins of their species distribution and the full distributional range. This gap in knowledge impedes the determination of detailed predictions for most species' futures. Over the course of four months, we investigated physiological changes (primary production, respiration, calcification and growth rates) of 6 populations of the intertidal ecosystem engineer and articulated coralline alga Corallina officinalis to future climatic conditions (low pH (∼7.8); T + 3 °C; as well as the combination of low pH and T + 3 °C). The populations (n = 2 per geographical location) represent the northern (Iceland) and southern (Spain) margins, as well as the centre (England) of the species distribution in the NE Atlantic. Here, we show that southern and central populations are already living closer to their thermal and stress limits, while Northern populations appear to be the most resilient to environmental changes. We present data confirming light calcification to be the most valuable physiological process which is prioritized in populations throughout the geographical gradient in the NE Atlantic. We found elevated temperature to have a greater effect on populations than pCO2. Investigating and monitoring organism physiology and structure under these extreme environmental conditions provides important information to predict their acclimatisation and resilience to future environmental conditions and potential changes in their distribution

Understanding the margin squeeze: Differentiation in fitness-related traits between central and trailing edge populations of Corallina officinalis

Assessing population responses to climate‐related environmental change is key to understanding the adaptive potential of the species as a whole. Coralline algae are critical components of marine shallow water ecosystems where they function as important ecosystem engineers. Populations of the calcifying algae Corallina officinalis from the centre (southern UK) and periphery (northern Spain) of the North Atlantic species natural distribution were selected to test for functional differentiation in thermal stress response. Physiological measurements of calcification, photosynthesis, respiration, growth rates, oxygen and calcification evolution curves were performed using closed cell respirometry methods. Species identity was genetically confirmed via DNA barcoding. Through a common garden approach, we identified distinct vulnerability to thermal stress of central and peripheral populations. Southern populations showed a decrease in photosynthetic rate under environmental conditions of central locations and central populations showed a decline in calcification rates under southern conditions. This shows that the two processes of calcification and photosynthesis are not as tightly coupled as previously assumed. How the species as whole will react to future climatic changes will be determined by the interplay of local environmental conditions and these distinct population adaptive traits

Dark respiration, primary production and calcification rates of the coralline alga Corallina officinalis L. under varying temperature conditions

Physiological rates of C. officinalis at the experimental irradiance, and in the dark in the 4 temperature treatments (C, HW, +3, HW+3) for the 3 incubation times (t1, before the MHW start; t2, right after the MHW end; t3, after a recovery period from the MHW end)