Tintinnoinea
Abundance patterns

The few data available suggest significantly different tintinnid concentrations between neritic and oceanic surface waters. In coastal environments such as the Bahía Blanca estuary, tintinnids may reach densities up to 11,300 ind. lö-1 (Barría de Cao, 1992). Such high densities are comparable to some reported for neritic waters of other regions: Narragansett Bay, 14,000 ind. lö-1 (Hargraves, 1981); Long Island Sound, 13,000 ind. lö-1 (Capriulo and Carpenter, 1983); estuary of the Tamar river, SW England, 16,000 ind. l-1 (Dale and Burkill, 1982); Maine Estuary, 7,000 ind. lö-1 (Sanders, 1987); Northern coast of Denmark, 15,000 ind. lö-1 (Cordeiro, 1995). Perhaps the highest tintinnid concentrations so far reported are in the Kiel Fjords: 215 million ind. lö-1 (Kils, 1993). This extreme value is attributed mainly to Stenosemella nucula, which was found to form micro-layers and micro-patches up to 340 mm thick (Kils, 1989, 1993).

In oceanic waters off the Argentine shelf (30-60°S, 55°W) concentrations hardly exceed 20 ind. lö-1 (Alder et al., unpublished). Low oceanic tintinnid abundances were also registered in the California Current (Beers and Stewart, 1967) and in the North Pacific Central Gyre (Beers et al., 1975), where mean values reach only 19 and 5 ind. lö-1, respectively. South of the Antarctic Convergence densities can be considerably higher: in neritic Antarctic waters of the Southern Weddell Sea peak tintinnid concentrations are approx. 1200 ind. lö-1 (Boltovskoy et al., 1989; Boltovskoy and Alder, 1992). High-latitude oceanic waters influenced by sea-ice are a unique habitat which supports diverse and abundant communities (Garrison et al., 1983, 1986; Garrison and Buck, 1989a, b; Garrison, 1991a, b; Garrison and Gowing, 1993; Garrison and Close, 1993). Thus, probably as a response to enhanced food availability, tintinnids here are more abundant than in extrapolar oceanic regions. The Weddell-Scotia Confluence (57-62°S, 49°W), for instance, hosts concentrations around 250 ind. lö-1 (Alder and Boltovskoy, 1993; Alder, 1995).