Benthic realm and its biotic composition is highly important in glacio-marine fjords, specially when considering the cryosphere dynamics and the resulting phenomena (sedimentation, resuspension, freshwater influx, inter alia).
Also, in Antarctic seasonal bays (i.e. Mackellar Inlet (King George Island, South Shetlands), where I've sampled macrobenthic communities for previous research (see: http://goo.gl/YOy16D)) pelagic realm also plays a key role in terms of primary production and its consequent influence on higher trophic levels.
It's certain that analysing the benthic composition is more predictive when trying to speculate future scenarios. I presumably assume that the Mackellar Inlet is mainly a benthic-controlled system. Nevertheless, in order to be sure of this hypothesis I should go further through an integrated analysis of both realms.
The protocol that my colleagues usually execute is: macrobenthic survey (van Veen grab 0.05m2), collect plankton with plankton nets, and measure abiotic variables like temperature, pH, conductivity, turbidity and marine currents patterns (speed & direction).
I'd like to know if there's any specific protocol pointing straightforward to my question. What other measurements should I consider?
Thanks for the help. Cheers.
∞BSc. Bernabé Moreno
http://goo.gl/YOy16D
Plenty of avenues to investigate which such a question: Microbiota, meiofauna, megafauna, sediment traps, video surveys, granulometry, stable isotope analysis or molecular foodweb tracking to assess the nature and strength of pelagic-benthic link. Spatial and temporal design will be important, the system may shift with seasonal/glacial changes.
Stable Isotopes are useful and perhaps even analysis of nutrients in the pelagos, benthos and key biota
Like Nasreen and Jeroen suggested I would explore stable isotopes such as the C/N ratio. I would also consider S (sulphur) as well since it's usually associated with benthos and sediments. Also redox and sulfides from the sediment, microphytobenthos etc. are interesting parameters to assess the state of the benthos.
You can use stable isotopes, but you need consideration differents stages life of the invertebrates to work with trophic levels. One preview identification of the alimentary components, by microscopy and lactophenol. Never use the same sampler for this, all separate.You can use stable isotopes in the sediments and organismes. And how explain Remi Sonier, you can use de redox and sulfides from the sediments, because bacterias. In the sediment is good you see the perifiton (stable isotopes the all in the sediment by filter). Never forget the organic matter, too. Good look!
I agree with the previous comments. Stable Isoptopes can be very useful. Carbon can be affected by methanogenesis, but particularly the sulfur signal can give some indication of benthic energy contributions, but you need to look at external and internal sources, isotope ratio of the various benthic infaunal species and nekton. knowing the ecology of the organisms will help, such as filter feeding vs deposit feeding, benthic vs pelagic foraging by nekton (stomach contents and isotopes). Is the system shallow and oxic enough for benthic photoautotrophy? any chance of looking at benthic oxygen (P/R) and nutrient fluxes?
The question is raised to know whether the aquatic ecosystem are controlled by top-down or bottom up mechanisms. In the case of top down control it is necessary to look at the tropic cascade, or in other words entire food web dynamics. If the system is controlled by bottom up mechanism it is necessary to examine the nutrient dynamics at sediment water interface, redox potential and anoxic nature is important in this regard. In the case of tropical aquatic systems ecosystems are controlled by both mechanisms.
Thank you all for your substantive comments. They're already being very useful to help me structure some kind of study. Cheers.
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