57. Mesograzer Impacts in Marine Vegetation

Organised by Alistair Poore (University of NSW) to be held at UNSW and Sydney Institute for Marine Sciences, Sydney. First meeting to be held 30 March - 3 April, 2009. Second meeting 2-3 February 2010 at UNSW

POTENTIAL PARTICIPANTS INCLUDE Alistair Poore - UNSW - mesograzer ecology and evolution, novel technique for field manipulation of amphipods Emmett Duffy - Virginia Institute of Marine Sciences (USA) - mesograzer ecology and evolution, seagrass and algal beds of eastern USA Graham Edgar - U Tasmania - seagrass and algal beds of temperate Australiaseagrass and algal beds of temperate Australia Veijo Jormalainen - U Turku (Finland) - mesograzer ecology and evolution, algal beds of the Baltic Sea Erik Sotka - College of Charleston (USA) - mesograzer ecology and evolution, temperate and tropical algal beds of eastern USA John Stachowicz - U California (USA) - positive interactions, biodiversity-ecosystem function relationships, algal beds of western USA Richard Taylor - U Auckland (NZ) - mesograzer ecology, algal beds of temperate New Zealand Mat Vanderklift - CSIRO Marine and Atmospheric Research - algal and seagrass beds of Western Australia, food webs in coastal ecosystems Pamela Reynolds - U North Carolina (USA)

GOAL

It is well known that herbivory is particularly intense in marine environments, with a higher proportion of primary productivity removed than in terrestrial habitats. Our understanding of grazer impacts, however, is largely limited to large herbivores (urchins, fish, gastropods) and the ecological role of highly abundant mesograzers (small invertebrates such as amphipods and isopods) in structuring benthic communities is poorly understood. This is despite their central role in nearshore marine food webs, where they are the key link in transferring primary production to fishes. These animals share several analogies with herbivorous insects in terrestrial systems, yet their impact on primary production has not been rigorously tested in the field.

The limited understanding of mesograzer impacts stems from practical difficulties in experimentally manipulating their abundance in field conditions. The use of exclusion cages is highly problematic due to the small mesh size needed to restrict movement by these small animals – leading to altered water flow, light levels and sedimentation.

The working group will jointly choose a series of specific research questions and develop a standardized, common methodology and analyses to be used across the various experimental sites [based on recent findings (Poore et al)].

We aim to answer the following specific questions:

1) What is the impact of mesograzers in algal and seagrass dominated habitats worldwide?
2) How does grazer impact vary with richness and identity of primary producers?
3) Does grazer abundance and composition predict impacts on community structure?

These are high impact questions as small grazing invertebrates are ubiquitous in nearshore marine (and freshwater) ecosystems, and are known to be key links from primary producers to higher trophic levels, including commercial fisheries. The new method of manipulating their densities in field conditions overcomes logistical difficulties that have seriously hampered rigorous tests of their top-down impacts on primary producer communities.

Last Updated January 2010