Human-induced salinity changes impact marine organisms and ecosystems

Climate change is fundamentally altering marine and coastal ecosystems on a global scale. While the effects of ocean warming and acidification on ecology and ecosystem functions and services are being comprehensively researched, less attention is directed toward understanding the impacts of human-driven ocean salinity changes. The global water cycle operates through water fluxes expressed as precipitation, evaporation, and freshwater runoff from land. Changes to these in turn modulate ocean salinity and shape the marine and coastal environment by affecting ocean currents, stratification, oxygen saturation, and sea level rise. Besides the direct impact on ocean physical processes, salinity changes impact ocean biological functions with the ecophysiological consequences are being poorly understood. This is surprising as salinity changes may impact diversity, ecosystem and habitat structure loss, and community shifts including trophic cascades. Climate model future projections (of end of the century salinity changes) indicate magnitudes that lead to modification of open ocean plankton community structure and habitat suitability of coral reef communities. Such salinity changes are also capable of affecting the diversity and metabolic capacity of coastal microorganisms and impairing the photosynthetic capacity of (coastal and open ocean) phytoplankton, macroalgae, and seagrass, with downstream ramifications on global biogeochemical cycling. The scarcity of comprehensive salinity data in dynamic coastal regions warrants additional attention. Such datasets are crucial to quantify salinity-based ecosystem function relationships and project such changes that ultimately link into carbon sequestration and freshwater as well as food availability to human populations around the globe. It is critical to integrate vigorous high-quality salinity data with interacting key environmental parameters (e.g., temperature, nutrients, oxygen) for a comprehensive understanding of anthropogenically induced marine changes and its impact on human health and the global economy.     

Seed size selection in heteromyids

Summary The general conclusion of this paper is that heteromyids do not select seed sizes on the basis of their body size. My conclusion comes from the analysis of new data from central New Mexico, analysis of data in the literature on food habits of heteromyids, and a reanalysis of Brown and Lieberman (1973) and Brown (1975). All of these sources agree that no seed size selection exists.Although no pattern of simple seed size selection was found, interesting differences were noticed among species. First, the tendency to husk appears to be related to the size of the rodent. Second, large heteromyids may depend on fruiting heads made up of small seeds. This may or may not have significance to the coexistece of heteromyid communities. At present, insufficient data are available to make conclusions along these lines.Intuitively satisfying hypotheses, such as seed size allocation by heteromyids, are normally very hard to lay to rest. It is my hope that this paper demonstrates the weight of evidece is against seed size allocation in heteromyids. Those who wish to maintain this hypothesis, or reveal that it or related hypotheses have anything to do with heteromyid coexistence, must now produce data to support their position.