Characterizations of how species mediate ecosystem properties require more comprehensive functional effect descriptors

Abstract

The importance of individual species in mediating ecosystem process and functioning is generally accepted, but categorical descriptors that summarize species-specific contributions to ecosystems tend to reference a limited number of biological traits and underestimate the importance of how organisms interact with their environment. Here, we show how three functionally contrasting sediment-dwelling marine invertebrates affect fluid and particle transport - important processes in mediating nutrient cycling - and use high-resolution reconstructions of burrow geometry to determine the extent and nature of biogenic modification. We find that individual functional effect descriptors fall short of being able to adequately characterize how species mediate the stocks and flows of important ecosystem properties and that, in contrary to common practice and understanding, they are not substitutable with one another because they emphasize different aspects of species activity and behavior. When information derived from these metrics is combined with knowledge of how species behave and modify their environment, however, detailed mechanistic information emerges that increases the likelihood that a species functional standing will be appropriately summarized. Our study provides evidence that more comprehensive functional effect descriptors are required if they are to be of value to those tasked with projecting how altered biodiversity will influence future ecosystems.

Mediation of macronutrients and carbon by post-disturbance shelf sea sediment communities

“…Sediment surface scrapes were taken to determine sediment particle size (Malvern Mastersizer 2000, Malvern Instruments; Supplementary Figures S1 and S2) and percentage organic carbon content (loss on ignition, 375°C, 1 h, Pansu and Gautheyrou 2006; org-C). Overlying seawater was replaced after 24 h to remove excess nutrients associated with assembly (Hale et al 2014). Aquaria were maintained at ambient bottom temperature (Irish Sea, June 2016), 14°C, in the dark and continually aerated at the School of Ocean Sciences, Bangor University for 7 days.…”

“…The maximum vertical deviation of the sediment-water interface (upper-lower limit = surface boundary roughness, SBR) provided an indication of surficial activity. Following Hale et al (2014), the mean ( f-SPI L mean , time dependent indication of mixing), median ( f-SPI L med , short-term depth of mixing), and maximum ( f-SPI L max , full extent of vertical mixing over the longterm) depths of particle redistribution were calculated using a custom-made semi-automated macro that runs within FIJI (Schindelin et al 2012;ImageJ, Version 1.47v Forster et al 1999). The sediment and associated macrofauna community (retained on 500 lm sieve) in each aquarium were fixed in a 10% formalin (4% formaldehyde) solution buffered with seawater (salinity, 33) on Day 7.…”

Vulnerability of macronutrients to the concurrent effects of enhanced temperature and atmospheric pCO2 in representative shelf sea sediment habitats

“…In contrast, mud communities were dominated by surficial modifiers and sand communities were dominated by biodiffusers under ambient conditions, but underwent considerable change in functional composition (mud: increase in conveyors, decrease in surficial modifiers; sand, reduction in biodiffusers, increase in surficial modifiers and conveyors) under future climatic conditions (Widdicombe et al 2009). It follows that the extent to which individual species or assemblages control biogeochemical processes will vary with environmental context (Godbold and Solan 2009) and depend upon the relevance and relative importance of individual functional traits to specific microbial processes and/or nutrient pathways (Murray et al 2014;Hale et al 2014;Botto et al 2005;Laverock et al 2010). We conclude, therefore, that the effects of climatic forcing on biogeochemical condition are predominantly expressed through functionally important changes in microbial and macrofaunal community structure, and their interactions (Gilbertson et al 2012), rather than via changes in carbonate chemistry and metabolism associated with an altered environment (Drupp et al 2016;Kim 2016).…”

“…From these data we calculated the mean ( f-SPI L mean ) and maximum ( f-SPI L max ) depths of particle redistribution. Following Hale et al (2014) we also determined surface boundary roughness (SBR, the maximum vertical deviation of the sediment water interface) as an indicator of surficial activity. Burrow ventilation was estimated from absolute changes in the concentration of the inert tracer sodium bromide…”

Oil spill effects on macrofaunal communities and bioturbation of pristine marine sediments (Caleta Valdés, Patagonia, Argentina): experimental evidence of low resistance capacities of benthic systems without history of pollution

“…They also highlight the need to carry out longer-term experiments in order to test the resilience capacities of this type of benthic system. A special attention to the shifts in macrobenthic species functional traits due to oil contamination should also be paid as they can markedly affect biogeochemical cycling with cascading effects on the ecological functioning of the whole ecosystem (Van Colen et al 2012;Hale et al 2014;Kristensen et al 2014). This knowledge is fundamental in developing an efficient environmental management strategy against pollutions particularly for sensitive pristine marine protected areas such as Caleta Valdés.…”