Eastern boundary current systems (EBUS) present contrasted levels of anoxia. A shallow oxycline reduces the habitat for most species, concentrating pelagic life within a thin surface layer. This is particularly significant at night when diel migrant organisms occupy the surface oxygenated layer to ‘pay their oxygen debt’. Such organisms’ concentration can enhance trophic interactions among...
Eastern boundary upwelling systems (EBUS) are among the most productive ecosystems on Earth. Chemical and biological processes in EBUS are strongly influenced by the sub- to anoxic conditions that are typically found in water masses below the productive surface layer. During February to April 2017 we conducted an in situ mesocosm experiment near Callao (Peru) to study the factors that...
The near-coastal zone boardering the Humboldt Current System is highly productive and has a high economic value for artesanal fisheries. However, it is under constant thread from low oxygen due to local decomposition processes, high plankton productivity and the already low oxygen content of the upwelling water mass. Zooplankton distribution in the Bahia Callao, a low oxygen bay in Central...
The functioning of Oxygen Minimum Zones in the Pacific remains debated. In particular, the fate of the OM is unclear owing to competing processes (preservation versus microbial activity). Recent high-vertical resolution in situ observations off Peru reveal an unexpected biogeochemical structuring in the oxygen minimum zone, potentially associated with a specific vertical particles distribution...
In the Peruvian Upwelling system, the mesopelagic oxygen minimum zone (OMZ) is the main vertically structuring feature of the pelagic habitat. Several zooplankton and nekton organisms undertake diurnal vertical migrations (DVMs) into anoxic depths. It has been argued that these migrations contribute substantially to the oxygen consumption as well as excretion of dissolved compounds (in...
Significant variability in zooplankton abundances and distributions, associated with very small differences in oxygen concentration and temperature, were documented at midwater depths within the strong oxygen minimum zone of the Eastern Tropical North Pacific in Jan – Feb 2017. First, a towed hydrographic profiler, the Wire Flyer, was deployed on ~50 km long transects between 325–650m or...
As a result of cultural eutrophication, bottom water hypoxia has been increasing globally in estuarine and shelf waters. Coastal hypoxia has the potential to adversely impact pelagic zooplankton communities by increasing the mortality of copepod eggs which can sink into low oxygen bottom waters. Using depth-specific sampling we examined the vertical distribution of copepod eggs and nauplii...
Zooplankton occupies an important role in pelagic ecosystems as it provides the link between primary producers and higher trophic levels and to a large extent shapes elemental cycles. Zooplankton organisms feed on all kinds of small particulate matter (e.g. phytoplankton, detritus, smaller zooplankton organisms) and egested fecal pellets contribute substantially to the passive sinking flux out...
The northern Benguela Upwelling System (nBUS) has been facing increasing temperatures and decreasing dissolved oxygen (DO) levels over the last decades. This has implications for key processes and trophic interactions within the ecosystem including shifts in community composition, distribution ranges, and trophic levels, changes in energy flows and migration patterns with feedbacks to...
In 2015, 5 stations each were sampled in the tropical Atlantic and the West-Sahara OMZ for mesopelagic fauna. Community analysis revealed a close relationship between OMZ and tropical region, although some species increased in abundance in the OMZ (e.g. Nannobrachium isaacsi, Myctophidae; Malacosteus niger, Malacosteidae). Length composition and size ranges revealed a smaller maximum...
Predicting the ecological impacts of deoxygenation for deep-sea communities on continental margins is challenging due to the difficulty of conducting community-level manipulative experiments in the deep sea. However, there is a pressing need to understand these impacts since oxygen is declining at midwater depths and continental margins are important habitats for demersal fish communities,...
The Gulf of Mexico experiences a large hypoxic area in the summer from nutrient loadings that originate from activities in the watershed. We are developing individual-based population models of croaker, menhaden, and shrimp to analyze how hypoxia effects on reproduction, growth, mortality, and movement of individuals leads to population-level responses. These population models are the last...
Estimating the effects of recurring seasonal hypoxia on the long-term composition, diversity, and functioning of macrobenthic communities on continental shelves is challenging because early 20th century monitoring surveys are rare and the sedimentary sequences in cores are mixed by bioturbation. Here, we evaluate the effects of eutrophication and frequent hypoxic events on macrobenthic...
In the Humboldt Current System water deoxygenation occurs naturally producing Oxygen Minimum Zones where the fauna usually present different levels of adaptations or tolerance to low oxygen conditions. The high variability of the system causes variability of hypoxia at different spatial and temporal scales throughout the HCS, and the responses of the seabed biota may be different between...
Mangroves naturally experience short-term dissolved oxygen (DO) fluctuations, making them susceptible to diel hypoxia. Hypoxia has adverse effects on aerobic organisms such as fish as it leads to physiological and behavioural altering community dynamics of marine animals.
DO is a fundamental parameter of water quality, but few studies have examined short-term changes of DO and the associated...
Although it is known that oxygen is critical to the biology, ecology and biogeochemical cycling of the oceans, and to the influence of the oceans on the earth’s climate, major uncertainties remain – especially in our ability to scale up from small spatial scales and short time periods to fish stocks, global oxygen patterns and future times. Continued research, observation analysis and...
Oxygen minimum zones (OMZs) are defined as water masses where O2 concentrations are <0.5 mL L-1 (<22µM). Permanent OMZs cover over 1 million Km2 of seafloor and intersect the continental margins of the Pacific, Indian and Atlantic Oceans. OMZs are predicted to expand in response to global warming. OMZ expansion has implications for food webs and ecosystem function through reorganization and...