ALBERT

Description: Salps have attracted attention as zooplankton organisms that may be able to expand their habitat range and increase their ecological importance in the face of ongoing global warming. Due to their gelatinous nature, unique feeding strategy, and reproductive ecology such changes could have profound impacts on regional marine ecosystems. While their role in the regional carbon cycle is receiving attention, our knowledge of their physiology and life cycle is still limited. This knowledge gap is mainly due to their fragile gelatinous nature, which makes it difficult to capture and maintain intact specimen in the laboratory. We present here a modified kreisel tank system that has been tested onboard a research vessel with the Southern Ocean salp Salpa thompsoni and at a research station with Salpa fusiformis and Thalia democratica from the Mediterranean Sea. Successful maintenance over days to weeks allowed us to obtain relative growth and developmental rates comparable to in situ field samples of S. thompsoni and S. fusiformis, and provided insights into previously unknown features of their life cycle (e.g., testes development). Our results show that traditional methods of estimating growth, such as cohort analysis, may lead to a general overestimation of growth rates and neglect individual strategies (e.g., shrinkage), which can affect the results and conclusions drawn from population dynamic models. By providing a starting point for the successful maintenance of different species, comparable experiments on the physiology of salps is made possible. This will contribute to refining model parameters and improving the reliability of the predictions.

Description: Abstract Proliferation of redundant terms in ecology and conservation slows progress and creates confusion. ‘Countryside biogeography’ has been promoted as a new framework for conservation in production landscapes, so may offer a replacement for other concepts used by landscape ecologists. We conducted a systematic review to assess whether the 'countryside biogeography' concept provides a distinctive framing for conservation in human‐dominated landscapes relative to existing concepts. We reviewed 147 papers referring to countryside biogeography and 81 papers that did not. These papers were divided into categories representing three levels of use of countryside biogeography concepts (strong, weak, cited only) and two categories that did not use countryside biogeography at all but used similar concepts including fragmentation and matrix. We revealed few distinctions among groups of papers. Countryside biogeography papers made more frequent use of the terms 'ecosystem services', 'intensification' and 'land sparing' compared with non‐countryside biogeography papers. Papers that did not refer to countryside biogeography sampled production areas (e.g. farms) less often, and this related to their focus on habitat specialist species for which patch‐matrix assumptions were reasonable. Countryside biogeography offers a conceptual wrapper rather than a distinctive framework for advancing research in human‐modified landscapes. This and similar wrappers such as ‘conservation biogeography’ and ‘agricultural biogeography’ risk creating confusion among new researchers, and can prevent clear communication about research. To improve communication, we recommend using the suite of well‐established terms already applied to conservation in human‐modified landscapes rather than through an interceding conceptual wrapper.

Description: Since the 1980s, the San Francisco Bay Delta ecosystem has experienced large declines in primary production. Hypothesized reasons for this decline include (1) suppression of nitrate (NO3−) uptake, and thus phytoplankton growth, due to high concentrations of ammonium (NH4+), and (2) wastewater NH4+-induced changes in phytoplankton community composition away from large-celled diatoms. These twin hypotheses implicate NH4+ loading from the Sacramento Regional Wastewater Treatment Plant effluent outfall in explaining declines in primary production in the region. They have been controversial within the water resources management community and have stimulated a lengthy public scientific and regulatory debate. Here, in an effort to resolve this debate, we present results from a 48-h incubation experiment with surface water from both upstream and downstream of the Sacramento Regional Wastewater Treatment Plant effluent outfall, a major source of NH4+ loading to the ecosystem. We amended this water with either NH4+, NO3−, or full wastewater effluent. All assays were incubated under high light (52% of incident irradiance) or low light (6% of incident irradiance). NO3− uptake rates were suppressed to near zero in all treatments with either added NH4+, added wastewater effluent, or high in situ NH4+ concentrations. Yet, phytoplankton uniformly grew well on all dissolved inorganic nitrogen sources, including effluent and NH4+. Diatom species were the most abundant taxa at all stations, and diatom cell abundances increased at greater rates than all other taxa over the course of the experiment. Among all treatments, the light treatment had the greatest effects on chlorophyll a accumulation and phytoplankton growth rates. Our results suggest that high NH4+ loading is not a driver of the lower productivity in the San Francisco Bay Delta. Although phytoplankton preferred NH4+ to NO3− when both were available in our experiment, the form of dissolved inorganic nitrogen had no effect on growth rates or species composition.