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Increasing jellyfish populations around the world may substantially impact seafloor habitats

Utskrift

- Jellyfish blooms are known to have significant impacts on local industries from causing massive fish kills in aquaculture cages to clogging water intake pipes used by power stations for cooling. However, as NIVA research scientist Dr. Andrew K. Sweetman explains, they may adversely affect ocean floor habitats as well.

Different factors such as climate change, over-fishing, cultural eutrophication, ballast water exchange and nutrient stress from aquaculture have been implicated in promoting greater frequencies of native and invasive jellyfish blooms throughout the world’s oceans.

Dead jellyfish release nutrients
- When jellyfish die, their decomposing carcasses sink and use up oxygen that most marine organisms use to respire, and release nutrients that can stimulate plant growth in the water column. This may pose a large problem to small enclosed fjords and pols around the world (e.g. Norway, Sweden) that receive very little water exchange and oxygen replenishment in the first place says Sweetman.

Since numerous jellyfish species often found around Norway, such as the Moon Jelly (Aurelia aurita) and Lions Mane (Cyanea capillata), possess annual life cycles, yearly blooms of these species mean that any impacts from them will most likely re-occur year-after-year.

Jellyfish bodies that are not decomposed in the water column and which reach the seafloor may cut off the supply of oxygen to sediment habitats and increase organic loads in the sediment – so-called ‘Jellyfalls’.

Dead jellyfish aggregations (left) and dead jellyfish slime (right) on the seafloor off the coast of Oman. (Photos courtesy of Dr. David Billett, NOCS, UK. Photos copywright of NOCS (National Oceanography Centre, UK)

Hunting for dead jellyfish in Lurefjorden
Despite the potentially large effects jellyfish blooms and associated jellyfalls may have on the benthic habitat, their precise impact on the seafloor is severely understudied and merits rigorous investigation.

This spring Andrew Kvassnes Sweetman and Dr. Karl Norling from NIVA, together with Dr. Annelise Chapman from Runde Environmental Centre will lead a study to investigate the deep-water and seafloor of Lurefjorden, and look for mass aggregations of dead or dying jellyfish on the seafloor.

- This fjord is estimated to have more than 50,000 tons of jellyfishes, but we don’t know what happens when they die. Some of the questions we want to find the answers to are if they are going to sink down to the bottom, what eats them, and what is their effect on animals living in the sediments, says research scientist Dr. Karl Norling.

Contact persons
Research Scientist Andrew Kvassnes Sweetman
Research Scientist Karl Norling

Funded project:
Dr. Andrew K. Sweetman and Dr. Karl Norling at NIVA have started a new, research initiative founded by NIVA. The project aim is to characterize jellyfish deposition and explore their impacts on seafloor ecosystems in the deep-fjords around southern Norway using the latest in tethered underwater photography techniques.

Partners:
Norwegian Institute for Water Research (Norway)
Runde Environmental Centre (Norway)
Akvaplan-NIVA (Norway)
National Oceanography Centre (UK)
Griffith University (Australia)
University of Hawaii (USA)

Project aims:
The partners in the project hope to collect a variety of data, such as jellyfish fall accumulation data, seafloor sediment chemistry, and invertebrate biodiversity in fjords dominated by jellyfish and those that do not support large jellyfish populations.

Future funding:
Dr. Andrew K. Sweetman and Dr. Karl Norling (NIVA), as well as Dr. Annelise Chapman from Runde Environmental Centre (Norway), Dr. Paul Renaud from Akvaplan-NIVA (Norway), Dr. Kylie Pitt from Griffith University (Australia), Dr. Dror Angel from the University of Haifa (Israel) and Dr. Dan Jones from the National Oceanography Centre (UK) and Prof. Craig Smith from the University of Hawaii (USA) have also begun to collaborate with the hope of funding and leading a larger research infrastructure to study the full impacts of jellyfish on a variety of pelagic/ seafloor ecosystems from shallow lagoons in the tropics to deep-sea ecosystems.

In conjunction with colleagues from the University College of Cork and Queens University Belfast in Ireland, Dr. Andrew K. Sweetman is in the process of also trying to secure funding for a project aimed at being able to predict jellyfish blooms by trying to correlate jellyfish abundance (quantified visually from ships of opportunity) to environmental data (sampled from same ship using NIVA’s very own FERRYBOX system).

By being able to predict jellyfish blooms effectively, an early warning system can be developed that can alert fish farmers and the local public of a potential jellyfish bloom so that immediate mitigation strategies can be implemented.

Should these research initiatives be funded, it seems that NIVA will become a leading research institute into the regional and global impacts of jellyfish blooms on the marine environment.

Publisert av: Hilde Marie Fougner
Sist oppdatert: 04/17/2009

Gaustadalléen 21, NO-0349 Oslo, tlf. 02348, fax. 22 18 52 00, niva@niva.no, nettredaktør: Hilde Marie Fougner