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Este artículo contiene 16 páginas, 10 figuras, 1 tabla., Global concern over increasing CO2 emissions, and the resultant CO2 driven temperature rises and changes in seawater chemistry, necessitates the advancement of understanding into how these changes will affect marine life now and in the future. Here we report on an experimental investigation into the effects of increased CO2 concentration and elevated temperature on sedimentary meiofaunal communities. Cohesive (muddy) and noncohesive (sandy) sediments were collected from the Eden Estuary in St. Andrews, Scotland, UK, placed within a flume setup and exposed to 2 levels of CO2 concentration (380 and 750 ppmv, current at the time of the experiment, and predicted CO2 concentration by 2100, respectively) and 2 temperature levels (12 °C and 16 °C, current in-situ and predicted temperature by 2100, respectively). We investigated the metazoan meiofauna and nematode communities before and after 28 days of exposure under these experimental conditions. The most determinative factor for abundance, diversity and community structure of meiofauna and nematodes was sediment type: on all levels, communities were significantly different between sand and mud sediments which agrees with what is generally known about the influence of sediment structure on meiofaunal organisms. Few CO2 and temperature effects were observed, suggesting that meiofauna and nematodes are generally much less responsive than, for instance, microbial communities and macrofauna to these environmental changes in estuarine environments, where organisms are naturally exposed to a fluctuating environment. This was corroborated by the observed effects related to the different seasons in which the samples were taken from the field to run the experiment. After 28 days, meiofauna and nematode communities in muddy sediments showed a greater response to increased CO2 concentration and temperature rise than in sandy sediments. However, further study is needed to investigate the underlying mechanisms and meiofauna species-specific resilience and responses to ocean acidification and warming, and their interactions with other biota, to understand what such changes may mean for meiofauna communities and the ecosystem processes and functions they contribute to., Authors acknowledge support through the NERC OA programme. PJS acknowledges support from the UK Natural Environment Research Council through National Capability funding and, with the Department for Environment, Food and Rural Affairs, through the Marine Ecosystems Research Programme (grant number NE/L003279/1). JI was supported by a Plymouth Marine Laboratory Post-doctoral Research Fellowship in collaboration with University of Exeter and a Marie Curie Intra-European Fellowship within the 7th European Commission Framework Programme (Grant Agreement FP7-PEOPLE- 2011-IEF no. 00879).

Curvilinear or distributional representations extract patterns of relative species abundances in an assemblage, encompassing a range of diversity information from evenness to richness, rather than reducing that information to a single summary statistic, such as a diversity index. In k-dominance curves the cumulative relative abundances of species, ranked in decreasing order of their importance in terms of abundance (or biomass), are plotted against species rank, or more usually log species rank. The higher the curve in a k-dominance plot, and the more quickly it reaches its maximum value (of 100), the lower the evenness and richness components of diversity. A modified logistic transformation of the y- (cumulative abundance) axis brings the values closer to linearity to enable easier visual comparisons. Partial dominance curves overcome the problem that the visual information presented is over-dependent on the single most dominant species. The statistical significance of differences between replicated sets of curves can be tested using multivariate methodologies.