Does climate change affect marine productivity?

Xabier Irigoien, doctor of Oceanography, has participated in more than 15 national and international programmes, 36 oceanographic campaigns and is the author or co-author of 36 articles in international magazines (SCI index).

The published work shows the results of the investigation done about the marine ecosystems and the relationship between plankton and fishing. In particular, the study analyses the model considered until the now as the classic food chain in marine ecosystems, which goes from primary production (phytoplankton) to fishing.

The study is based on the research done with copepods and their young (nauplius), which constitute the food of larvaes and adults of a series of fish of commercial interest, such as codfish, anchovies, sardines, etc. This work has analysed the relationship between the composition of phytoplankton and the copepod egg hatching in very relevant and highly productive areas for fishing, such as the cost of Namibia, el Labrador, Island, Norway or the North Sea.

The research team that has done this study sets their work under the international programme known as GLOBEC. The fundamental objective of this programme is to understand how climate change affects the abundance, diversity and productivity of marine populations, and, specially, to understand how global change affects fishing of commercial interest. With this objective, GLOBEC focuses on the study of zooplankton. Why zooplankton? Because these small animals floating in the ocean are the transmission chain between vegetal production and fishing production.

Algaes are not toxic

Copepods are microscopic animals that live in the sea. It is an important part of marine food chain, as they are the main food source for fish. Therefore, the existence of many copepods it is essential in order to exist a lot of fish.

Similarly, copepods eat phytoplankton. Phytoplankton consists of several microscopic algae and the most important are diatoms. Hence, diatoms, copepods and fish form an important food chain in the marine ecosystem.

Several researches have been done with copepods and diatoms in laboratories, and in some of them, it has been suggested that diatoms affect the copepod egg hatching. Apparently, diatoms may produce a toxic compound for copepod eggs.

Irigoien and the scientist group under his supervision have analysed if something similar occurs in nature, that is, if the increase of the population of diatoms in sea affects the copepod egg hatching.

Those diatom samples have been compared with hatching rates of copepod and no significant relationship has been found between hatching success and diatoms. So why do diatoms affect copepods in laboratory? There can be two reasons for a lower hatching success in the laboratory: on the one side diatoms may be nutritionally deficient, and, as a consequence, if copepods just eat diatoms, their hatching success reduces. On the other side, the type of diatoms copepods eat may be toxic under laboratory conditions.

Anyway, this research has proved that nothing similar happens in nature; so diatoms have no negative effect on food chain.

Elhuyar Fundazioa

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Does climate change affect marine productivity?

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