By the pulsed nature of their life cycles, gelatinous zooplankton come and go seasonally, giving rise in even the most undisturbed circumstances to summer blooms. Even holoplanktonic species like ctenophores increase in number in the spring or summer when planktonic food is available in greater abundance. Beyond that basic life cycle-driven seasonal change in numbers, several other kinds of events appear to be increasing the numbers of jellies present in some ecosystems. Over recent decades, man’s expanding influence on the oceans has begun to cause real change and there is reason to think that in some regions, new blooms of jellyfish are occurring in response to some of the cumulative effects of these impacts. The issue is not simple and in most cases there are few data to support our perceptions. Some blooms appear to be long-term increases in native jellyfish populations. A different phenomenon is demonstrated by jellyfish whose populations regularly fluctuate, apparently with climate, causing periodic blooms. Perhaps the most damaging type of jellyfish increase in recent decades has been caused by populations of new, nonindigenous species gradually building-up to ‘bloom’ levels in some regions. Lest one conclude that the next millennium will feature only increases in jellyfish numbers worldwide, examples are also given in which populations are decreasing in heavily impacted coastal areas. Some jellyfish will undoubtedly fall subject to the ongoing species elimination processes that already portend a vast global loss of biodiversity. Knowledge about the ecology of both the medusa and the polyp phases of each life cycle is necessary if we are to understand the true causes of these increases and decreases, but in most cases where changes in medusa populations have been recognized, we know nothing about the field ecology of the polyps.

https://faculty.washington.edu/cemills/jellyblooms2001.pdf

Jellyfish blooms: are populations increasing globally in response to changing ocean conditions?

Introduction. Alien Species in European Waters Leppakoski, et al. Bioinvasion Ecology: Assessing Invasion Impact and Scale Carlton. Who is Who Among Nonindigenous Species. Protists - A Dominant Component of the Ballast-Transported Biota Hulsmann, Galil. Introduced Marine Algae and Vascular Plants in European Aquatic Environments Wallentinus. Coscinodiscus wailesii - A Nuisance Diatom in European Waters Laing, Gollasch. The Comb Jelly Mneniopsis leidyi in the Black Sea Kideys. The Predatory Water Flea Cercopagis pengoi in the Baltic Sea: Invasion History, Distribution and Implications to Ecosystem Dynamics Telesh, Ojaveer. History and Success of an Invasion into the Baltic Sea: The Polychaete Marenzelleria cf. viridis, Development and Strategies Zettler, et al. Alien Crayfish in Europe: Negative and Positive Impacts and Interactions with Native Crayfish Westman. Invasion History, Biology and Impacts of the Baikalian Amphipod Gmelinoides fasciatus Panov, Berezina. Ponto-Caspian Amphipods and Mysids in the Inland Waters of Lithuania: History of Introduction, Current Distribution and Relations With Native Malacostracans Arbaciauskas. Teredo navalis - The Cryptogenic Shipworm Hoppe. Introduction and Acclimatisation of the Pacific Carpet Clam, Tapes philippinarum, to Italian Waters Breber. Dreissena (D.) polymorpha: Evolutionary Origin and Biological Peculiarities as Prerequisites of Invasion Success Orlova. Zebra Mussel: Impacts and Spread Minchin, et al. Red King Crab (Paralithodes camtshaticus) and Pink Salmon (Oncorhynchus gorbuscha) in the Barents Sea Petryashov, et al. Alien Freshwater Fishes of Europe Lehtonen. Introduced Semiaquatic Birds andMammals in Europe Nummi. Genetics on Invasive Species Muller, Griebeler. Vectors. Vectors -- How Exotics Get Around Minchin, Gollasch. Oyster Imports as a Vector for the Introduction of Alien Species into Northern and Western Europe Coastal Waters Wolff, Reise. Exotics for Stocking and Aquaculture, Making Correct Decisions Minchin, Rosenthal. Life in Ballast Tanks Gollasch, et al. Ballast Tanks Sediments Hamer. Regional Overviews. Biological Invasions in the White Sea Berger, Naumov. Introduced Marine Organisms in Norwegian Waters, Including Svalbard Hopkins. The Baltic Sea -- a Field Laboratory for Invasion Biology Leppakoski, et al. Introduced Marine Species of the North Sea Coasts Reise, et al. Exotics of Coastal and Inland Waters of Ireland and Britain Minchin, Eno. Open Atlantic Coast of Europe -- A Century of Introduced Species Goulletquer, et al. Review of Non-native Marine Plants in the Mediterranean Sea R. Siguan. Current Status of Aquatic Introductions in Italy O. Ambrogi. A Sea Change -- Exotics in the Eastern Mediterranean Sea Galil, Zenetos. The Marmara Sea, A Link Between the Mediterranean and the Black Sea Ozturk. The Black Sea -- A Recipient, Donor and Transit Area for Alien Species Gomoiu, et al. Invaders in the Caspian Sea Aladin, et al. Invasions by Alien Species in Inland Freshwater Bodies in Western Europe: The Rhine Delta van der Velde, et al. Biological Invasions into German Waters: An Evaluation of the Importance of Different Human-mediated Vectors for Nonindigenous Macrozoobenthic Species Nehring. Invasive Ponto-Caspian Species in Waters of the Vistula and Oder Basins and the Southern Baltic Sea Jazdzewski, Konopacka. The

Invasive Aquatic Species of Europe - Distribution, Impacts and Management

The North Atlantic portunid crab Carcinus maenas (Linnaeus, 1758) has invaded the North Pacific Ocean following more than two centuries of global dispersal due to human activities. C. maenas was first collected in San Francisco Bay, California, in 1989–1990, where its distribution and prey selectivity were investigated in 1992–1994. It has become abundant in shallow, warm lagoons (which as favorable and retentive microhabitats may have served as invasion incubators) and spread throughout the north, central and south bays. It may have arrived in ballast water, on fouled ships, amongst algae with imported live bait or lobsters, or by intentional release; genetic comparisons of the Bay population with possible source populations may aid in defining the transport mechanism. C. maenas' eurytopic nature, its high breeding potential, and its diet and feeding behavior suggest the potential for extensive ecosystem alterations through predator-prey interactions, competition, disturbance, and indirect effects. Although both negative economic impacts through reduction or disruption of fisheries and positive impacts of providing bait and human-food fisheries have been documented in a few regions, the potential economic impacts in San Francisco Bay remain largely unknown.

Introduction, dispersal and potential impacts of the green crab Carcinus maenas in San Francisco Bay, California

The introduction of non-indigenous species (NIS) across the major European seas is a dynamic non-stop process. Up to September 2004, 851 NIS (the majority being zoobenthic organ- isms) have been reported in European marine and brackish waters, the majority during the 1960s and 1970s. The Mediterranean is by far the major recipient of exotic species with an average of one introduction every 4 wk over the past 5 yr. Of the 25 species recorded in 2004, 23 were reported in the Mediterranean and only two in the Baltic. The most updated patterns and trends in the rate, mode of introduction and establishment success of introductions were examined, revealing a process similar to introductions in other parts of the world, but with the uniqueness of migrants through the Suez Canal into the Mediterranean (Lessepsian or Erythrean migration). Shipping appears to be the major vector of introduction (excluding the Lessepsian migration). Aquaculture is also an important vector with target species outnumbered by those introduced unintentionally. More than half of immigrants have been estab- lished in at least one regional sea. However, for a significant part of the introductions both the establishment success and mode of introduction remain unknown. Finally, comparing trends across taxa and seas is not as accurate as could have been wished because there are differences in the spatial and taxonomic effort in the study of NIS. These differences lead to the conclusion that the number of NIS remains an underestimate, calling for continuous updating and systematic research.

/pdf/globalisation-in-marine-ecosystems-the-story-of-non-2h0x6kri8p.pdf

Globalisation in marine ecosystems : The story of non-indigenous marine species across European seas

During the past several decades, high numbers of gelatinous Zooplankton species have been reported in many estuarine and coastal ecosystems. Coupled with media-driven public perception, a paradigm has evolved in which the global ocean ecosystems are thought to he heading toward being dominated by “nuisance” jellyfish. We question this current paradigm by presenting a broad overview of gelatinous Zooplankton in a historical context to develop the hypothesis that population changes reflect the human-mediated alteration of global ocean ecosystems. To this end, we synthesize information related to the evolutionary context of contemporary gelatinous Zooplankton blooms, the human frame of reference for changes in gelatinous Zooplankton populations, and whether sufficient data are available to have established the paradigm. We conclude that the current paradigm in which it is believed that there has been a global increase in gelatinous Zooplankton is unsubstantiated, and we develop a strategy for addressing the critical questions about long-term, human-related changes in the sea as they relate to gelatinous Zooplankton blooms.

/pdf/questioning-the-rise-of-gelatinous-zooplankton-in-the-world-51f8599cgl.pdf

P.Y. Sorokin

Papers

A newly acclimated species in the Black Sea: The ctenophore Mnemiopsis leidyi (Ctenophora: Lobata)