Arturas Razinkovas

The Relevance of Marine Chemical Ecology to Plankton and Ecosystem Function: An Emerging Field

Marine chemical ecology comprises the study of the production and interaction of bioactive molecules affecting organism behavior and function. Here we focus on bioactive compounds and interactions associated with phytoplankton, particularly bloom-forming diatoms, prymnesiophytes and dinoflagellates. Planktonic bioactive metabolites are structurally and functionally diverse and some may have multiple simultaneous functions including roles in chemical defense (antipredator, allelopathic and antibacterial compounds), and/or cell-to-cell signaling (e.g., polyunsaturated aldehydes (PUAs) of diatoms). Among inducible chemical defenses in response to grazing, there is high species-specific variability in the effects on grazers, ranging from severe physical incapacitation and/or death to no apparent physiological response, depending on predator susceptibility and detoxification capability. Most bioactive compounds are present in very low concentrations, in both the producing organism and the surrounding aqueous medium. Furthermore, bioactivity may be subject to synergistic interactions with other natural and anthropogenic environmental toxicants. Most, if not all phycotoxins are classic secondary metabolites, but many other bioactive metabolites are simple molecules derived from primary metabolism (e.g., PUAs in diatoms, dimethylsulfoniopropionate (DMSP) in prymnesiophytes). Producing cells do not seem to suffer physiological impact due to their synthesis. Functional genome sequence data and gene expression analysis will provide insights into regulatory and metabolic pathways in producer organisms, as well as identification of mechanisms of action in target organisms. Understanding chemical ecological responses to environmental triggers and chemically-mediated species interactions will help define crucial chemical and molecular processes that help maintain biodiversity and ecosystem functionality.

Alien Malacostracan Crustaceans in the Eastern Baltic Sea: Pathways and Consequences

The recent invasion history of malacostracan crustaceans into the eastern Baltic Sea is reviewed with 16 alien species being recorded from the easternmost area. These invasives constitute 3% of the total species richness (50% of the alien biota), and comprise up to 80% of the total benthic biomass in several localities. The Ponto-Azov-Caspian species are the most diverse and abundant component. Their taxonomical and ecological dominance could be explained by a combination of factors including similarities between the Baltic, the donor regions and the waterway network that allows their dispersal. The high vulnerability of the Baltic Sea to invasion may be a consequence of low native biodiversity coupled with anthropogenic and natural factors. The potential impact of alien Malacostraca on the native community was assessed following predatory studies of alien amphipods on native benthic biota. These studies indicated that the alien amphipods may alter the structure of their prey communities. Alien crustaceans have outnumbered or even completely replaced native species and/or earlier established invaders locally in the eastern Baltic Sea.

Revision pre-ingestive selection efficiency definition for suspension feeding bivalves: facilitating the material fluxes modelling

The importance of the particle selective feeding of bivalves becomes more evident and it is necessary to incorporate this phenomenon into ecological models in order to reflect correctly the material fluxes inside the organism and ecosystem as well. The problems related to the modelling of organic matter selection are considered in this paper and a new definition of pre-ingestive selection efficiency is proposed. It differs from the classical one in using the organic material fraction in ingested food instead of pseudofaeces. The newly defined selection efficiency exhibits an advantage in simplified shape of experimental relationship to the organic matter fraction in seston and easier derivation of formulas related to mathematical food processing formulation.

Linking NPZD and foodweb models of an estuarine lagoon ecosystem

Among aquatic ecosystems, estuarine lagoons are generally more complex than inland waters because of the combined effect of the land and the sea. These systems are under the influence of land through the rivers and have a restricted and temporally variable water exchange with the seas or the oceans. Estuarine lagoons are generally productive ecosystems which offer habitats for many species. Many coastal and estuarine lagoons are known to be important components of the natural capital providing opportunities for aquaculture. These ecosystems are difficult to analyze. Like most of the transitional waters, their trophic and ecological status cannot be defined easily because of their complexity. Most of them are usually under strong human influence or already modified heavily, which makes this task even more difficult. Nutrient phytoplankton zooplankton detritus (NPZD) models can help scientists to analyze the full picture of an aquatic system, together with physical, chemical and biological processes, to fill in the gaps of data between samplings and to forecast environmental changes and use this output for planning. Traditionally, these models have been developed and used by engineers extensively, usually with the aim of water resources and quality management. However, different needs may arise in ecological studies with different aims such as better understanding how an aquatic ecosystem works or analyze the interactions in an aquatic food web. In this case, different state variables may be needed than the conventional ones, which are used by more general water quality models that are available. In ecological studies, related to coastal lagoon ecosystems organism groups on the higher trophic levels can be of interest. In this study, an NPZD model and a trophic network model that contains organism groups on the higher trophic levels were linked using the ldquobottom-up controlrdquo approach. Such a linkage of models provides the possibility to use the advantages of both models; reproducing of the erratic behavior of nutrients and plankton as realistic as possible, while still taking the more complex organisms in the trophic network, which respond to external forcing in a larger time scale. The models developed in this study were applied to the Curonian Lagoon that is an important estuarine ecosystem for Lithuania.

Decision Making, Policy And Financing

Abstract: The most critical situation facing the health of water resources and aquatic ecosystems is not the result of a single activity on or near a lake, river, or stream. Instead, it is the combined and cumulative result of many individual activities throughout a waterbody?s entire natural drainage area, catchment area or watershed. A watershed is the area of land where all of the water that is under it or drains off of it goes into the same place. John Wesley Powell, U.S. scientist and geographer, put it best when he said that a watershed is: ?that area of land, a bounded hydrologic system, within which all living things are inextricably linked by their common water course and where, as humans settled, simple logic demanded that they become part of a community. World-wide watersheds supply drinking water, provide recreation and respite, and sustain life. Throughout the world, countries depend on clean water and healthy watersheds for food, fiber, manufactured goods, and tourism. This natural capital is the basis for social economic systems in developed and developing countries and the building block for the future in undeveloped countries. In the United States more than

Assessment of the effects of variation in external nutrient loads on the Curonian lagoon ecosystem

450 billion in food and fiber, manufactured goods, and tourism depends on clean water and healthy watersheds. Watersheds come in all shapes and sizes. They cross county, state, and national boundaries. No matter where you are, you are in a watershed! As we all live in a watershed, our individual actions can directly affect it. The cumulative effects of all the individual actions of everyone within a watershed may be, and often are devastating to the quality of water resources and affect the health of living things including humans. Management for sustained use of water and other ecosystem resources requires a watershed based approach.

Seasonality of Coastal Phytoplankton in the Baltic Sea: Influence of Salinity and Eutrophication

Curonian lagoon, the largest coastal lagoon in Europe is characterized by the strong seasonal and interannual variation in nutrient loads and water quality parameters is characterized by the dominance of the Nemunas rivers discharges. Coupled hydrodynamic and NPZD model was applied to assess the impacts of the foreseen reduction of nutrient loads prescribed in the State Plan to Improve the Quality in the Curonian lagoon, which was approved in 2006. The simulation of 1999-2000 was used as the background scenario. The NPZD model applied takes into the account the recently evaluated atmospheric nitrogen fixation by the cyanobacteria during the summer ldquobloomsrdquo and combined effects of temperature and wind climate.