Predation risk triggers copepod small-scale behavior in the Baltic Sea.

Predators not only have direct impact on biomass but also indirect, non-consumptive effects on the behavior their prey organisms. A characteristic response of zooplankton in aquatic ecosystems is predator avoidance by diel vertical migration (DVM), a behavior which is well studied on the population level. A wide range of behavioral diversity and plasticity has been observed both between- as well as within-species and, hence, investigating predator-prey interactions at the individual level seems therefore essential for a better understanding of zooplankton dynamics. Here we applied an underwater imaging instrument, the video plankton recorder (VPR), which allows the non-invasive investigation of individual, diel adaptive behavior of zooplankton in response to predators in the natural oceanic environment, providing a finely resolved and continuous documentation of the organisms' vertical distribution. Combing observations of copepod individuals observed with the VPR and hydroacoustic estimates of predatory fish biomass, we here show (i) a small-scale DVM of ovigerous Pseudocalanus acuspes females in response to its main predators, (ii) in-situ observations of a direct short-term reaction of the prey to the arrival of the predator and (iii) in-situ evidence of pronounced individual variation in this adaptive behavior with potentially strong effects on individual performance and ecosystem functioning.

Correction: Community ecology in 3D: Tensor decomposition reveals spatio-temporal dynamics of large ecological communities.

[This corrects the article DOI: 10.1371/journal.pone.0188205.].

Community ecology in 3D: Tensor decomposition reveals spatio-temporal dynamics of large ecological communities.

Understanding spatio-temporal dynamics of biotic communities containing large numbers of species is crucial to guide ecosystem management and conservation efforts. However, traditional approaches usually focus on studying community dynamics either in space or in time, often failing to fully account for interlinked spatio-temporal changes. In this study, we demonstrate and promote the use of tensor decomposition for disentangling spatio-temporal community dynamics in long-term monitoring data. Tensor decomposition builds on traditional multivariate statistics (e.g. Principal Component Analysis) but extends it to multiple dimensions. This extension allows for the synchronized study of multiple ecological variables measured repeatedly in time and space. We applied this comprehensive approach to explore the spatio-temporal dynamics of 65 demersal fish species in the North Sea, a marine ecosystem strongly altered by human activities and climate change. Our case study demonstrates how tensor decomposition can successfully (i) characterize the main spatio-temporal patterns and trends in species abundances, (ii) identify sub-communities of species that share similar spatial distribution and temporal dynamics, and (iii) reveal external drivers of change. Our results revealed a strong spatial structure in fish assemblages persistent over time and linked to differences in depth, primary production and seasonality. Furthermore, we simultaneously characterized important temporal distribution changes related to the low frequency temperature variability inherent in the Atlantic Multidecadal Oscillation. Finally, we identified six major sub-communities composed of species sharing similar spatial distribution patterns and temporal dynamics. Our case study demonstrates the application and benefits of using tensor decomposition for studying complex community data sets usually derived from large-scale monitoring programs.

A spatially explicit risk approach to support marine spatial planning in the German EEZ.

An ecosystem approach to marine spatial planning (MSP) promotes sustainable development by organizing human activities in a geo-spatial and temporal context. (1) This study develops and tests a spatially explicit risk assessment to support MSP. Using the German exclusive economic zone (EEZ) of the North Sea as a case study area, current and future spatial management scenarios are assessed. (2) Different tools are linked in order to carry out a comprehensive spatial risk assessment of current and future spatial management scenarios for ecologic and economic ecosystem components, i.e. Pleuronectes platessa nursery grounds. With the identification of key inputs and outputs the suitability of each tool is tested. (3) Here, the procedure as well as the main findings of the spatially explicit risk approach are summarised to demonstrate the applicability of the framework and the need for an ecosystem approach to risk management techniques using geo-spatial tools.