Monitoring and modelling marine zooplankton in a changing climate.

Zooplankton are major consumers of phytoplankton primary production in marine ecosystems. As such, they represent a critical link for energy and matter transfer between phytoplankton and bacterioplankton to higher trophic levels and play an important role in global biogeochemical cycles. In this Review, we discuss key responses of zooplankton to ocean warming, including shifts in phenology, range, and body size, and assess the implications to the biological carbon pump and interactions with higher trophic levels.

Regenerated iron: How important are different zooplankton groups to oceanic productivity?

The scarcity of iron limits phytoplankton growth in large areas of the global ocean. Zooplankton may contribute to the cycling of iron via excretion and egestion. Despite evidence of high iron content in zooplankton excretion and faecal products, many questions arise as to the availability of regenerated iron for phytoplankton growth.

Resource Colimitation Drives Competition Between Phytoplankton and Bacteria in the Southern Ocean.

Across the Southern Ocean, phytoplankton growth is governed by iron and light, while bacterial growth is regulated by iron and labile dissolved organic carbon (LDOC). We use a mechanistic model to examine how competition for iron between phytoplankton and bacteria responds to changes in iron, light, and LDOC. Consistent with experimental evidence, increasing iron and light encourages phytoplankton dominance, while increasing LDOC and decreasing light favors bacterial dominance.

Nutrient Cycling: Are Antarctic Krill a Previously Overlooked Source in the Marine Iron Cycle?

Iron limits phytoplankton growth in large areas of the Southern Ocean. A new study shows that Antarctic krill play a crucial role in the recycling of iron in the iron-limited waters.

The biogeochemical role of baleen whales and krill in Southern Ocean nutrient cycling.

The availability of micronutrients is a key factor that affects primary productivity in High Nutrient Low Chlorophyll (HNLC) regions of the Southern Ocean. Nutrient supply is governed by a range of physical, chemical and biological processes, and there are significant feedbacks within the ecosystem. It has been suggested that baleen whales form a crucial part of biogeochemical cycling processes through the consumption of nutrient-rich krill and subsequent defecation, but data on their contribution are scarce.

A global experiment suggests climate warming will not accelerate litter decomposition in streams but might reduce carbon sequestration.

The decomposition of plant litter is one of the most important ecosystem processes in the biosphere and is particularly sensitive to climate warming. Aquatic ecosystems are well suited to studying warming effects on decomposition because the otherwise confounding influence of moisture is constant. By using a latitudinal temperature gradient in an unprecedented global experiment in streams, we found that climate warming will likely hasten microbial litter decomposition and produce an equivalent decline in detritivore-mediated decomposition rates.