The physiological definition for stress is: a specific response by the body to a stimulus, as fear or pain, which disturbs or interferes with the normal physiological equilibrium of an organism. (credit: Dictionary.com unabridged v 1.0.1) http://dictionary.reference.com/search?q=stress&x=33&y=12
From left to right:Low tide at the beach of Ambleteuse credit photograph: http://www.mincoin.com; Predation of a gobbie by a lizardfish credit photograph: http://www.explorebiodiversity.com/Hawaii/Shrimp-goby/general/Predators.htm; Seal caught in a plastic net credit photograph: http://eprentice.sdsu.edu/J03CW/rutter/ocean/index.html
In the marine environment, organisms are constantly under different conditions of stress as desiccation on the shore, high light, high temperatures near the hydrothermal vents, low nutrients, predation, pollution, etc. There are in fact many different kinds of stresses that have different origins. Marine organisms have developed adaptations to the stresses they undergo. Organisms living on the shore (e.g. mussels) have developed adaptation to resist to desiccation by retaining water for example. Some types of algae (e.g. many species of Fucus) can loose about 80% of their normal concentration of water and still survive to the low tide period.
From left to right: Scientists measuring the primary production of microphytobenthos on the soft shore © Yann Fontana, Station biologique de Roscoff. Result of a microarray experiment (for more information go to microarrays) © Jonas Collen, Station biologique de Roscoff
Studying stress and response to stress is important regarding the global changes (e.g. climate warming, oceans’ acidification, etc.) the Earth is starting to undergo. In fact, because marine organisms are so well adapted to their environment, a slight change in their environment can have an effect on them and change the organisation of the ecosystems. It is therefore important to be able to understand stress responses to evaluate the level of stress organisms are under and how this might evolve. Being able to look into the genes of the organisms, thanks to genomics, can enable researchers to understand these responses better. In fact, functional genomics experiments enable to see which genes are involved in which response mechanism.
From left to right : "Black smoker at a mid-ocean ridge hydrothermal vent."
Image ID: nur04506, National Undersearch Research Program (NURP) Collection Location: Atlantic Ocean Photographer: P. Rona Credit: OAR/National Undersea Research Program (NURP); NOAA". Giant tubeworms Riftia pachyptila photographed at 2 630 meters deep during an oceanographic cruise in 2002, credit photograph: www.planete-energies.com. The alvinellid polychate, Alvinella pompejana credit picture: IFREMER
The discovery of hydrothermal vents in the 1970’s at about 2,100 meters deep on the eastern Pacific dorsal has revealed the existence of organisms living in extreme conditions of stress. In fact, these organisms have developed adaptations to high temperature (up to 360 °C), low levels of oxygen and hydrocarbonates, presence of heavy metals and sulphated products that are considerably more concentrated than during pollution peaks on the coasts. To know more about hydrothermal species and adaptation to extreme conditions, click on the link.
Studying stress responses in marine organisms is interesting to population genetists as understanding how a body can adapt to a stressful situation can give insight on the understanding of the spatial distribution of populations for instance. In fact, knowing what level of stress a population is able to endure is part of its life history traits and can explain why it is located at a given place in the environment. see population genetics
The brown alga Laminaria digitata
Credit photograph: http://www.hippocratus.com/pages/detail_plante.asp?ID=lam002
Studying the molecular aspects of the responses to stress can enable scientists to discover new molecules. These new molecules can have different potential applications. For example, enzymes called haloperoxidases involved in defence mechanisms in the brown alga Laminaria digitata have been discovered. These enzymes are involved in the iodine uptake of the alga which has the capacity to concentrate this compound at very high rates (about 30 000 times the outside concentration). Iodine plays an important role in human health and the discovery of such molecules is therefore interesting concerning research in that field. For more detailed information about the studies performed on this alga, click on the following link: Laminaria digitata
Genomics, proteomics and functional analyses are being performed by scientists within the network ‘Marine Genomics Europe’ to evaluate the impact of global changes on marine organisms, communities and ecosystems at a greater resolution than was previously possible. The aim of these studies is to be able to predict changes in population structure resulting from specific new or more intense stressful elements and to produce tools to assess stress levels in specific ecological niches.
Contributed by Stephanie Ries
