Abstract
Seafloor biodiversity is a key mediator of ecosystem functioning, but its role is often excluded from global budgets or simplified to black boxes in models. New techniques allow quantification of the behavior of animals living below the sediment surface and assessment of the ecosystem consequences of complex interactions, yielding a better understanding of the role of seafloor animals in affecting key processes like primary productivity. Combining predictions based on natural history, behavior of key benthic species and environmental context allow assessment of differences in functioning and process, even when the measured ecosystem property in different systems is similar. Data from three sedimentary systems in New Zealand illustrate this. Analysis of the behaviors of the infaunal ecosystem engineers in each system revealed three very different mechanisms driving ecosystem function: density and excretion, sediment turnover and surface rugosity, and hydraulic activities and porewater bioadvection. Integrative metrics of ecosystem function in some cases differentiate among the systems (gross primary production) and in others do not (photosynthetic efficiency). Analyses based on behaviors and activities revealed important ecosystem functional differences and can dramatically improve our ability to model the impact of stressors on ecosystem and global processes.
Highlights
As large positive and negative pulses (a3)
For example for nutrient fluxes, is it sediment turnover by bulldozing organisms with associated disruption of the porewater and changes in surface topography[30] or direct porewater pressurization by advective bioirrigation with little or no sediment grain movement[26] or is it just the excretion rates of very large and numerous organisms? The spatial dynamics associated with specific behaviors are very different; bulldozing directly causes grain and porewater movements near to the animal’s body and alters surface topography, while pressurization of porewater can cause water movement several body lengths beyond the pressure source[15,23,26]
Our fundamental thesis is that based on knowledge of the natural history, animal behavior, and sediment characteristics, all of which are fine scale species driven metrics, we can predict the drivers of ecosystem function in systems dominated by one of the above ecosystem engineer species
Summary
As large positive and negative pulses (a3). Part (b) Austrovenus exhibits weak effects on porewater pressures: burrowing results in positive and negative pulses similar to those of Macomona but much smaller; feeding is accompanied by sharp, small positive pulses that often result from closure of the excurrent siphon and apparent opening of the pedal gape, perhaps for removal of material from the labial palps[38] (b1). Our fundamental thesis is that based on knowledge of the natural history, animal behavior, and sediment characteristics, all of which are fine scale species driven metrics, we can predict the drivers of ecosystem function in systems dominated by one of the above ecosystem engineer species. New techniques, such as porewater pressure sensors, allow us to quantify the impacts of fine scale, species specific behaviors in ways that generate predictions of magnitudes of such important integrated components of ecosystem function as ammonium efflux. We can test our predictions with published field measurements in systems dominated by each of the three ecosystem engineers
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