Section

The zooplankton time series Helgoland in the German Bight, about 60 km from the German mainland (54 11’N 7 54’E) is a high-frequency monitoring programme that has been investigating the phenology and dynamics of meso- and macrozooplankton at the Helgoland Reede Observatory since 1975. The programme was originally started in 1974 by Wulf Greve at the Biological Institute Helgoland and later continued in cooperation with the Federal Maritime and Hydrographic Agency, the Alfred Wegener Institute for Polar and Marine Research and the DZMB.

In addition to zooplankton data, the sampling includes a phytoplankton time series (since 1962) as well as time series for inorganic nutrients, salinity and temperature and several shorter time series (e.g. chlorophyll and other data from ferry box systems).

The high sampling frequency of the Helgoland Reede time series provides a unique opportunity to study long-term trends in abiotic and biotic parameters, but also ecological phenomena such as seasonal interactions between different components of the food web. At the same time, early detection of invasive species is enabled.

Zooplankton are small animals that spend their lives drifting with ocean currents. They play an essential role in marine ecosystems, transferring energy from phytoplankton to fish as well as birds and whales. Building a fundamental link changing plankton communities will inevitably affect the whole ecosystem.

In light of global warming and pressures on marine systems from human activities measurements of zooplankton biodiversity are urgently needed to set baselines and provide comprehensive analyses on ecosystem states. In recent decades various standard programs started to monitor changes within zooplankton communities. However, morphological identification of zooplankton is time-consuming, demands comprehensive taxonomic knowledge and has been shown to often underestimate true diversity due to occurrence of many cryptic species. Thus, there is a crucial need for fast, easy-to-use and inexpensive assessment tools. The application of species-specific proteomic mass profiles measured by MALDI-TOF MS (matrix-assisted laser/desorption ionization time-of-flight mass spectrometry) has strong potential to serve as fast method for species discrimination. Compared to metabarcoding this method requires less time, less expensive consumables and less specialized personnel. The overall aim of our project is to evaluate the general possibility and feasibility of estimating biodiversity by proteomic fingerprinting as a species identification tool in zooplankton with calanoid copepods as a model taxon. We assess the dimension of variability of proteome fingerprints within and between species using different life stages and populations. The general applicability of the method in ecosystems with an unknown number of undescribed species will be examined in a case study on deep sea benthopelagic copepods. As an important part of this project, we establish a proteome fingerprint reference library as well as integrated morphological and molecular taxonomic reference library entries for calanoid copepods to facilitate the species identification for experts and non- taxonomist. The project is part of the DFG priority program SPP 1991 Taxon-Omics (https://www.taxon-omics.com) with a funding period from 2018-2021.

Calanoid copepods, which live in the benthopelagial directly above the sea floor in the deep sea from 3000m, form a very diverse group in this ecosystem. Due to the difficulties of sampling this habitat, very little is known about the biodiversity of the benthopelagic calanoids, their distribution or their ecology.

Since the end of the 20th century, the introduction and use of modern equipment for sampling the seabed has made it possible to study the deep-sea biotic communities. Catching devices like the epibenthic sledge, which is used on research vessels like Polarstern or Meteor, or the American deep-sea diving robot ALVIN allow unique sampling, and bring to light a high number of new and rare taxa. In recent years it has been shown that the biodiversity of calanoid copepods in the deep sea close to the bottom is comparable to many pelagic ecosystems. However, most of the species occurring in the benthopelagial are new and not yet described. The identification and description of new species is done integratively by morphological and molecular methods. The phylogeny of calanoid copepods is investigated using molecular markers such as COI, cyt b, ITS2, 18s and 28s.

Calanoid copepods play a key role in marine food webs as they are the main food source for many commercially exploited fish species. As grazers on phytoplankton they transfer energy from primary production to higher trophic levels. Any change at the copepod community level therefore has consequences for the entire marine food web.

Characteristics in population dynamics, such as reproductive time and potential, growth or mortality rates are important parameters to describe the life cycle of calanoid copepods, to estimate secondary production and to draw conclusions about the influence of the life cycle of calanoid copepods on the recruitment and population dynamics of commercially exploited fish.

We investigate the impact of changes in the physical environment on growth, development and mortality of individual copepod species (Pseudocalanus elongatus, Acartia tonsa) from the North and Baltic Seas in experimental studies in-situ on board research vessels and on animals from laboratory cultures.

These studies provide information on whether the species occurring in the North Sea and Baltic Sea are capable in the long term of adapting to changes in their environment and maintaining a population in the areas under study, or whether environmental changes are causing migration or extinction of various species.