ALBERT

Description: The production of defence metabolites is assumed to be costly in metabolic terms. If this holds true, low-light stress should reduce the ability of seaweeds to defend themselves chemically against herbivory and fouling. We investigated the effect of energy limitation on the defensive status of seaweeds by assessing their attractiveness to mesograzers and their activity against a bivalve macrofouler in comparison with non-stressed conspecifics. The macroalgae Codium decorticatum (Woodw.) M. Howe, Osmundaria obtusiloba (C. Agardh) R. E. Norris, Pterocladiella capillacea (S. G. Gmel.) Santel. and Hommer., Sargassum vulgare C. Agardh and Stypopodium zonale (Lamour.) Papenf. collected at the southeastern Brazilian coast were exposed to six levels of irradiation (between 1 and 180 μmol photons m−2 s−1) for 10–14 days. After this period, algae from all treatment levels were: (a) processed as artificial food and offered to an amphipod community dominated by Elasmopus brasiliensis Dana and (b) extracted to test for differences in settlement rates of the fouling mussel Perna perna L. on filter paper loaded with the crude extracts. Generally, photosynthesis rates and growth were reduced under low light conditions. Attractiveness to herbivores and macrofoulers, however, was insensitive to energy limitation. We discuss possible explanations for the observed absence of a relationship between light availability and algal defence including the change in nutritional value of the algal tissue, the allocation of resources towards defence instead of growth and the absence of costs for defence.

Description: The present study is a comprehensive comparison of the biochemical composition (protein, lipid, glycogen and cholesterol contents, and amino acid and fatty acid profiles) of 14 species of cephalopods with different life strategies (benthic, nektobenthic, benthopelagic and pelagic) in distinct habitats (neritic, demersal, oceanic and deep sea), with special emphasis placed on a male Architeuthis sp. The giant squid showed a significantly lower protein and total amino acid content in the gonad and digestive gland. The major essential amino acids were leucine, lysine and arginine. The major non-essential amino acids were glutamic acid, aspartic acid and proline. The benthopelagic cirrate octopus Opisthoteuthis sp. showed a lower content of these nitrogen compounds in the muscle. In respect to lipid and fatty acid contents, the giant squid showed the highest values in the gonad and digestive gland and the lowest in the muscle. Most of saturated fatty acid content was presented as 16:0; monounsaturated fatty acid content, as 18:1 and 20:1; and polyunsaturated fatty acid content, as 20:4n-6, 20:5n-3 and 22:6n-3. The highest cholesterol content in the gonad was detected in Opisthoteuthis sp. and Architeuthis sp.; in the digestive gland. in Todarodes sagittatus; and in the muscle, in Sepia elegans. The highest glycogen value in the gonad was detected in Octopus vulgaris; in the digestive gland and muscle, the highest values were attained in Opisthoteuthis sp. The relationships between life strategies and biochemical composition were investigated and principal component analysis (PCA) was performed. The different cephalopod life strategies could be well separated on the basis of the first two principal components. The nektobenthic and pelagic strategies were clearly separated from the benthic, suggesting that these groups of species are characterized by lower lipid content and higher protein content in the gonad. A rather similar life-strategy distinction was obtained for the digestive gland. The benthopelagic strategy was also well separated from benthic and pelagic strategies and from Architeuthis sp. In the muscle, the results indicated lower nitrogen and carbon compound contents in Architeuthis sp. and Opisthoteuthis sp. The environmental conditions that possibly explain the Architeuthis sp. stranding, the relationships between biochemical compositions and the life strategies of the different cephalopod species studied are discussed.

Description: Cephalopods are highly sensitive to environmental conditions and changes at a range of spatial and temporal scales. Relationships documented between cephalopod stock dynamics and environmental conditions are of two main types: those concerning the geographic distribution of abundance, for which the mechanism is often unknown, and those relating to biological processes such as egg survival, growth, recruitment and migration, where mechanisms are sometimes known and in a very few cases demonstrated by experimental evidence. Cephalopods seem to respond to environmental variation both ‘actively’ (e.g. migrating to areas with more favoured environmental conditions for feeding or spawning) and ‘passively’ (growth and survival vary according to conditions experienced, passive migration with prevailing currents). Environmental effects on early life stages can affect life history characteristics (growth and maturation rates) as well as distribution and abundance. Both large-scale atmospheric and oceanic processes and local environmental variation appear to play important roles in species–environment interactions. While oceanographic conditions are of particular significance for mobile pelagic species such as the ommastrephid squids, the less widely ranging demersal and benthic species may be more dependent on other physical habitat characteristics (e.g. substrate and bathymetry). Coastal species may be impacted by variations in water quality and salinity (related to rainfall and river flow). Gaps in current knowledge and future research priorities are discussed. Key research goals include linking distribution and abundance to environmental effects on biological processes, and using such knowledge to provide environmental indicators and to underpin fishery management.

Description: The variability of the Atlantic Meridional Overturning Circulation (AMOC) and the Meridional Freshwater Transport (Mov) at 24°N, 11°S, and 30°S, simulated with the GFDL-CM3 model under the historical (1860–2005) and RCP 4.5 and 8.5 scenarios (2006–2100) are examined. The results are compared with the climatology and observations in the search for salinity biases that would compromise the accuracy of the state of the future climate predicted by this model. The AMOC wavelet analysis shows a predominant decadal variability at 24°N, whereas the annual signal is more prominent in the South Atlantic. The Mov magnitude varies considerably among the latitudes: increasing at 24°N, rather stable at 11°S and decreasing at 30°S. Such a pattern is followed by an AMOC weakening regardless of the latitude until the end of the 21st century, indicating that a reduction in Mov in the southern South Atlantic and an increase in the North Atlantic are potential drivers of the AMOC destabilization. Both model and observations agree on the stability of the circulation, even though the model projects a stronger AMOC than the latter. Besides the AMOC weakening, a shoaling of its upper limb is also observed. Salinity biases were found mostly in the South Atlantic in the upper 1000 m of the water column, with the model results significantly deviating from the observations and climatology in the mid-Atlantic, especially at 30°S. Possible causes for the abovementioned results, including potential drivers for salinity biases are discussed.

Description: While most coastal communities are expected to, or have been, negatively impacted by climate change, cephalopods have generally thrived with shifting ocean conditions. However, whilst benefitting from the same physiological flexibility that characterizes cephalopods in general, cuttlefish have depth constraints imposed by the presence of a cuttlebone and are limited to specific locations by their particularly low vagility. To evaluate the potential effects of marine climate change on cuttlefish, Species Distribution Models (SDM) were applied to nine species of genus Sepiidae to assess potential changes to their future distribution (2050 and 2100), under four representative concentration pathway (RCP) scenarios (i.e., RCP 2.6, 4.5, 6.0, and 8.5; CMIP5). We show that future cuttlefish habitat suitability and distribution will potentially decrease. The species with the most extreme impacts, Doratosepion braggi (Verco, 1907), was observed to decline as much as 30.77% in average habitat suitability (from present 55.26% to 24.48% at RCP 8.5 in 2100), to Sepia officinalis Linnaeus, 1758 with a low maximum decrease of 1.64% in average habitat suitability (from present 59.62% to 57.98% at RCP 8.5 in 2100). Increases in habitat suitability were projected mostly at higher latitudes, while habitat decrease was predicted for the tropical regions and lower latitudinal limits of species’ distributions. As their habitats decrease in terms of habitat suitability, cuttlefish may not benefit from future changes in climate. Additionally, as potential “sea canaries” for coastal ecosystems, we may see many species and habitats from these systems affected by climate change, particularly in tropical regions.