|Fig.: Mnemiopsis leidyi A. Agassiz from the Caspian Sea (photo Tamara Shiganova)|
Non-native invasive species represent a significant threat to biodiversity and their ecological impacts are difficult to reverse. Stakeholders may like to protect natural resources to maintain biodiversity. Decisions require to quantify its status, trends and threats.
This case study considers the biodiversity decrease in the Caspian Sea following the invasion of the Mnemiopsis Leidyi specie.
Particularly, a sharp decrease was recorded in species diversity, abundance and biomass of zooplankton, as well as direct preys of Mnemiopsis.
The understanding of the biodiversity changes requires to monitor the ecosystem state through regular in site surveys.
|Fig.: Seasonal spatial distribution of Mnemiopsis leidyi (after Shiganova et al, 2004)|
It is seen that the highest inter-annual variability is observed for chlorophyll concentration, especially in the Southern Caspian where the coefficient of variation is more than 35% whereas it is less than 11% in the Northern Caspian.
The reason of that is the Mnemiopsis leidyi invasion: in 2001 the Chlorophyll annual mean increased by a factor of 1.1-1.2 as compared with 1998-1999.
|Fig.: Monthly averaged Chlorophyll concentration changes in 2005 (SeaWIFS data|
Ocean color onservations from the SeaWIFS satellite were also archived to support research studies.