A suite of parallel anthropogenic changes affects contemporary marine ecosystems. Excessive carbon dioxide (CO2) pollution results in warmer, more acidic oceans with lower dissolved oxygen (DO) levels, meanwhile the emission of reactive nitrogen/phosphorus results in eutrophication, excessive microbial degradation and thus metabolic hypoxia and acidification. Despite decades of empirical research how each individual stressor of the ‘climate-change syndrome’ (i.e., temperature, CO2, DO) affects the fitness of marine organisms, we still know little about the combined effects of these stressors. This lecture gives an overview over the nascent field of multi-stressor approaches evaluating the climate sensitivity of marine organisms across taxa. In most studied cases, combined effects of these stressors exceeded those observed individually. Effects of combined warming, acidification, and deoxygenation have mostly been additive (no stressor interaction) or synergistically negative (stressor interaction). The occurrence and strength of synergistic stressor interactions in some species, life history stages, and traits comprises a vexing challenge but hints at potentially greater sensitivities of organisms to marine climate change than previously recognized. This lecture is intended for post-secondary students, providing them with illustrated examples from the most resent literature, while aiding in communicating the urgent need for empirical data from multi-stressor approaches.
…in the true sense has kept biologist’s head scratching for quite some time, and matters have only gotten more complex since the thunderous advent of genetic methods. Yet the distinction between a species and – say – an ecotype of a species is more than just academic quibble.
In the case of the key silverside, Menidia conchorum, a species that is only found in the hypersaline ponds on the Florida Keys, it’s quite literally an existential question. So far, the protocols and steps of protection apply only in cases of threatened species, which is perhaps something that ought to change.
O’Leary et al. went down to the Florida Keys and sampled the silversides in order to compare them morphologically and genetically to the ‘parent’ species, the tidewater silverside Menidia peninsulae. Their findings show that key silversides are distinct, but not quite their own species yet. In addition, the study revealed the large amount of inbreeding and genetic drift that is happening in each of these small hypersaline ponds.
The paper concludes that although ‘only’ an ecotype, the key silverside is threatened by loss of habitat and therefore still needs our protection!