Marine Research Findings of the VECTORS Project

This website provides access to the research results of the VECTORS project, which can be used to support marine management decisions, policies and governance as well as future research and investment. VECTORS was a large scale project that brought together more than 200 expert researchers from 16 different countries. It examined the significant changes taking place in European seas, their causes, and the impacts they will have on society.

Variability in gelatinous zooplankton in the north-western Mediterranean Sea

Gelatinous zooplankton responds at different temporal and spatial scales to environmental changes. A set of factors has been argued as explanation of jellyfish increase in the Mediterranean Sea during the last decades: temperature increase, fishing, eutrophication, etc.12 The major part of studies have been done considering long series of samples collected at one or very few stations or, over a grid of samples in a period of time. The main objective of this study was to consider a wide range of sampling, both spatial and temporal, to build a new approach that enhance a better understanding of gelatinous zooplankton response to environmental changes. Zooplankton samples analysed covered the continental shelf and slope of the Catalan Coast, in the North-western Mediterranean (Fig. 1) mostly carried out during the spring and summer seasons when the highest abundance and biodiversity of gelatinous plankton are present in this region.


Sea water temperature increase affected both density and biodiversity of gelatinous zooplankton.

Interannual variability in gelatinous zooplankton density and biodiversity has been observed during two consecutive years, July 2003 and 2004. During 2003, an exceptionally warm year (almost 2ºC higher than 2004), lower mean density of both gelatinous (28 ± 189 ind/1000m3) and non-gelatinous (rest of zooplankton groups; 3562 ± 4559 ind/10m3) zooplankton was found compared to 2004 (gelatinous: 73 ± 644 ind/1000m3, non-gelatinous: 12645 ± 14029 ind/10m3) (Fig. 1). However gelatinous species biodiversity (species richness) was higher in the warmest year (50 vs. 44) mainly due to mayor number of Antho- and Leptothecata species (hydromedusae with benthic polyp stage), suggesting that temperature may affect hydromedusae life cycles. At higher water temperature more polyp-species released their free-swimming medusae to the water column probably because some species advanced their budding time and they overlapped. A total of 67 species has been found in the area with some new records to be described. Highest biodiversity spots were found associated to submarine canyons presence in the northern part of the studied area and to both nutrient rich water discharge from the Ebro River and warmer water mass in the southern part.


High physical variability constrained abundance species and population of gelatinous zooplankton.

High spatio-temporal variability has been observed for gelatinous zooplankton associated to high physical variability in the studied area (i.e. location of both the shelf-slope salinity front and the northern thermal front, canyon influenced dynamics, continental fresh water discharges). Large changes in distribution and abundance of both siphonophora and hydromedusae were found related to specific physical factors, revealing a high physical-biological coupling. In the case of the shelf-slope front, when it was located over the shelf acted as a barrier limiting the distribution of gelatinous plankton towards the open sea and concentrating it on the coastal side of the front, but allowing offshore plankton dispersion when the front was over the slope (see Figure 2 as example).


Unexpected jellyfish biodiversity in the NW Mediterranean.

The Hydrozoa fauna of the NW Mediterranean is one the most studied and best known of the world34. Even that, we still found new species for the science using common sampling techniques (zooplankton nets). This had been possible to the knowledge and experience of the research team and it should be due to important environmental changes in the last decades that could influence the higher probability of catch them in areas where before they did not inhabit or probably were scarce and increased their abundance recently.

This is the first time that an extensive survey of gelatinous zooplankton in a wide spatial and temporal range has been performed

Relevance for Policy:
  • Alien Invasive Species Directive
  • Convention on Biological Diversity
  • EU Biodiversity Strategy


Lead Author:

Elena Guerrero, Josep-Maria Gili and Ana Sabatés & Elena Guerrero
Agrocampus Ouest (AGRO)
Date of research: October 2014

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Risk assessment of sea urchin fishery in an MPA

Social economic impact assessment for the future 

Spatial overlap and recruitment success of cod 

Species richness, abundance in North Atlantic fish

The Atlantis model for the Sicily Strait fisheries 

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 266445
© Vectors 2015. Coordinated by Plymouth Marine Laboratory.