engleski

Jellyfish outbreaks: natural cycle or stress response effect?

The overall characteristic of the subtropical marine environment is its dynamic component of seasonality and consequent fluctuations in the abundance of plankton organisms. Under "regular" conditions we can talk about colder and warmer season characterised by successive alteration of particular populations in phytoplankton and zooplankton community. Generally, such of temporal change is known as an annual ecological cycle. Appearance/disappearance of plankton populations do not correspond only to annual periods but also to longer time scale. When (medium term or long term cycles) populations, in any time cycles, appear in a known (average?) abundance we consider it as a "regular conditions". At higher densities we consider such appearance as a bloom. A plankton bloom could be defined as: "A dense concentration of plankton individuals which occurs in response to optimum growth conditions" (Sumich, 1988). An open question is: "what is a dense concentration?" Whatever concentration we would take as an average, additional number of plankton individuals would probably be considered as "abnormal", "irregular", "unexpected" or "exceptional". These events strongly bias the functionality of marine ecosystem and therefore attract wide public curiosity, but the causes of blooms and the mechanisms involved are still a subject of debate among specialist.

jellyfish; hormesis; stress

nije evidentirano