ALBERT

Description: This is a laboratory experiment, carried out in Helgoland to explore how responses to the time scale and magnitude of fluctuations in environmental variables depend on the choice of time reference frame. The experiment consisted of exposing larvae of an intertidal invertebrate, Hemigrapsus sanguineus to different initial feeding periods (in days; food = freshly hatched Artemia sp Nauplii provided ad libitum), followed by a period without food. An ovigerous female of H. sanguineus was collected by hand in the intertidal of Helgoland (SW beach: “Kringel”; coordinates: 54.177323°N, 7.885273°E) during low tide on the 15th October 2020. It was kept until larval hatching in an aquarium (vol = 2 L with a shelter) at salinity = 32 ppt, temperature = 18°C, photoperiod 12:12, permanent oxygenation and fed every second day (from frozen shrimp); water was changed every day. Experiments started on date 31st October 2020 (day 0 of the feeding period). The feeding protocol was carried out with groups of freshly hatched zoea I larvae (3 replicates of 10 larvae each) at 4 temperatures (15, 17, 19, 21°C). Larvae were reared at salinity = 32 ppt. The response variables were developmental time (in days) and the number of larvae reaching the second zoeal stage. Additional columns provide calculations of the average duration of development depending on temperature and the proportion of feeding time given as a proportion of the full developmental time.

Description: portfolio available for a species to cope with and mitigate effects of climate change. Here, we quantified variation in larval survival and physiological rates of Carcinus maenas among populations occurring in distant or contrasting habitats (Cádiz: Spain, Helgoland: North Sea, Kerteminde: Baltic Sea). During the reproductive season, we reared larvae of these populations, in the laboratory, under a combination of several temperatures (15–24 °C) and salinities (25 and 32.5 PSU). In survival, all three populations showed a mitigating effect of high temperatures at lower salinity, with the strongest pattern for Helgoland. However, Cádiz and Kerteminde differed from Helgoland in that a strong thermal mitigation did not occur for growth and developmental rates. For all populations, oxygen consumption rates were driven only by temperature; hence, these could not explain the growth rate depression found at lower salinity. Larvae from Cádiz, reared in seawater, showed increased survival at the highest temperature, which differs from Helgoland (no clear survival pattern), and especially Kerteminde (decreased survival at high temperature). These responses from the Cádiz population correspond with the larval and parental habitat (i.e., high salinity and temperature) and may reflect local adaptation. Overall, along the European coast, C. maenas larvae showed a diversity of responses, which may enable specific populations to tolerate warming and subsidise more vulnerable populations. In such case, C. maenas would be able to cope with climate change through a spatial portfolio effect.

Description: 〈jats:p〉Climate change combined with anthropogenic stressors (e.g. overfishing, habitat destruction) may have particularly strong effects on threatened populations of coastal invertebrates. The collapse of the population of European lobster (〈jats:italic〉Homarus gammarus〈/jats:italic〉) around Helgoland constitutes a good example and prompted a large-scale restocking program. The question arises if recruitment of remaining natural individuals and program-released specimens could be stunted by ongoing climate change. We examined the joint effect of ocean warming and acidification on survival, development, morphology, energy metabolism and enzymatic antioxidant activity of the larval stages of the European lobster. Larvae from four independent hatches were reared from stage I to III under a gradient of 10 seawater temperatures (13–24°C) combined with moderate (∼470 µatm) and elevated (∼1160 µatm) seawater 〈jats:italic〉p〈/jats:italic〉CO〈jats:sub〉2〈/jats:sub〉 treatments. Those treatments correspond to the shared socio-economic pathways (SSP), SSP1-2.6 and SSP5-8.5 (i.e. the low and the very high greenhouse gas emissions respectively) projected for 2100 by the Intergovernmental Panel on Climate Change. Larvae under the elevated 〈jats:italic〉p〈/jats:italic〉CO〈jats:sub〉2〈/jats:sub〉 treatment had not only lower survival rates, but also significantly smaller rostrum length. However, temperature was the main driver of energy demands with increased oxygen consumption rates and elemental C:N ratio towards warmer temperatures, with a reducing effect on development time. Using this large temperature gradient, we provide a more precise insight on the aerobic thermal window trade-offs of lobster larvae and whether exposure to the worst hypercapnia scenario may narrow it. This may have repercussions on the recruitment of the remaining natural and program-released specimens and thus, in the enhancement success of future lobster stocks.〈/jats:p〉