Work Package 7
Adaptation of macrozoobenthic species to fluctuating oxygen concentrations and their effect on benthic fluxes
The core areas of oxygen minimum zones (OMZs) have been subject to studies concerning ecological consequences of permanent low oxygen (e.g. Diaz & Rosenberg 2008). The boundaries of OMZs, however, have not been considered as intensely despite their importance with regard to climate change and expansion of OMZs (Helly & Levin 2004). Several studies concluded that organisms that are able to simultaneously cope with potentially long-lasting hypoxic periods and intense oxygen input e.g. by upwelling events, can build up high densities and biomass if food supply is abundant (Levin 2003). Given the high variety of adaption mechanisms to these conditions, successful organisms in and along OMZs likely rely not only on one mechanism, but rather combine several strategies such as, for example, morphological and behavioral traits. In general, the boundaries of the Benguela Upwelling System have been poorly investigated in terms of species inventory, but during preliminary investigations we have observed that certain species occur with highest biomass directly at the edges of the OMZ. Therefore, we now aim to address the question:
General Questions and Research topics:
- By which mechanisms and up to which extent can abundant macrobenthic species survive fluctuations in oxygen availability and how does their activity affect benthic fluxes?
To clarify this, we will initially investigate the distribution of macrobenthic organisms along the transect with changing availability of oxygen in the bottom water. In addition, we will assess the abundance of macrobenthic species in the in situ and ex situ experiments planned to quantify benthic fluxes. This will reveal how the composition and activity of benthic macro organisms affect the fluxes between the sediment and water column. Furthermore, we will conduct targeted incubation experiments with selected, highly abundant species to determine how long they can survive without oxygen and their activity under fluctuations of oxygen availability on different time and concentration scales. This will contribute important boundary conditions for implementation of bioturbation in the benthic modelling work.