O L R ( 1981 ) 28 t 12) E. Biological O c e a n o g r a p h ) 883

'Intensive grazing initially caused an increase of the heterogeneity but ultimately resulted in a homo- geneous vegetation with a very low percentage cover...an almost total disappearance of the above- ground parts of the plant.' Centraalbureau voor Schimmelcultures, Oosterstraat 1, 3742 SK Baarn, Netherlands. (mwf)

81:6660 Robertson, D.R. and N.V.C. Polunin, 1981. Coex-

istence: symbiotic sharing of feeding territories and algal food by some coral reef fishes from the western Indian Ocean. Mar. Biol., 62(2/3):185- 195.

Cohabitation, previously undocumented, is reported between 1 damselfish and 2 surgeonfish species with the latter providing most of the interspecific defense. The net cost of sharing food and habitat with a damselfish (a tenth the size of a surgeonfish) appears to be very low; the cost of excluding it would be great. Such a relationship provides a means of coexistence under the same limiting resource con- ditions. Smithsonian Tropical Res. Inst., Apartado 2072, Balboa, Republic of Panama. (ahm)

81:6661 Smith, N.P:, 1981. Energy balance in a shallow

seagrass flat for winter conditions. Limnol. Oceanogr., 26(3):482-491.

Air-sea heat exchange processes are studied in a representative embayment on the Gulf of Mexico. Exchanges of sensible and latent heat energy account for most of the observed daily temperature changes. These energy fluxes are correlated with the passage of atmospheric fronts. Harbor Branch Foundation, Inc., RR 1, Box 196, Fort Pierce, Fla. 33450, USA. (mcs)

E80. Plankton (also p r i m a r y product iv i ty , seston and detr i tus)

81:6662 Booth, B.C., Joyce Lewin and R.E. Norris, 1981.

Silicified cysts in North Pacific nanoplankton. Biol. Oceanogr., 1(1):57-80.

Nine new forms of nanoplankton, possibly choano- flagellate cysts, have been seen only under SEM. 'At some stations these were the most abundant plank- tonic cells.' Cell walls consisted of 8 siliceous plates in 2 basic patterns. Includes micrographs. Dept. of Oceanog., Univ. of Washington, Seattle, Wash., USA. (mwf)

81:6663 Cadre, G.C., 1980. Reappraisal of the production and

import of organic carbon in the western Wadden Sea. Neth. J. Sea Res., 14(3/4):305-322.

Pronounced spatial and short-term temporal vari- ations in phytoplankton primary production make estimates imprecise, but it appears that particulate plus dissolved organic C imported from the North Sea and the IJsselmeer surpasses in-situ production. IJsselmeer POC may be an important food source for Wadden Sea invertebrates. Neth. Inst. for Sea Res., P.O. Box 59, 1790 AB Den Burg, Texel, Netherlands. (slr)

81:6664 Gagnon, Marc and Guy Lacroix, 1981. Zooplankton

sample variability in a tidal estuary: an interpreta- tive model. LimnoL Oceanogr., 26(3):401-413.

Copepods from 347 zooplankton hauls made from l m above the bottom to the surface at a 175-h anchor station in the St. Lawrence Estuary varied over time mostly in 'semidiurnal fluctuations superimposed on a long term trend.' A mathematical model showed that with a longitudinal gradient present all current tidal constituents were related to sample variability; local effects of a sill and an internal tide were contributory. Bio-Conseil Inc., 105 cote de la Montagne, suite 101, Quebec, Canada. (mwf)

81:6665 Greenwood, J.G., 1980. Composition and seasonal

variations of zooplankton populations in Moreton Bay, Queensland [Australia]. Proc. R. Soc. Qd, 91:85-103. Zool. Dept., Univ. of Queensland, Australia.

81:6666 Hammer, R.M., 1981. Day-night differences in the

emergence of demersal zooplankton from a sand substrate in a kelp forest. Mar. Biol., 62(4):275- 280.

Biomass and abundance of total demersal zoo- plankton (in two 12-hr sampling periods) were significantly higher in night samples and showed no significant differences between high (75 cm above bottom) and low (25 cm above bottom) trap collections. Continental Shelf Assoc., Inc., P.O. Box 3609, Tequesta, Fla. 33458, USA. (ahm)

81:6667 Hamner, W.M. and I.R. Hauri, 1981. Long-distance

horizontal migrations of zooplankton (Scyphome- dusae: Mastigias). Lirnnol. Oceanogr., 26(3):414- 423.