La Saline Research Articles

Mass Settlement and Post-Settlement Mortality of Epinephelus Merra (Pisces: Serranidae) On Réunion Coral Reefs

An unusual mass settlement event of the grouper Epinephelus merra occurred on the fringing coral reefs of Reunion Island (south-western Indian Ocean) in April 1994. This major event coincided with stormy conditions associated with the new moon period. The abundance of new settlers was surveyed for 45 days following settlement on both the reef flat and the back reef area of the coral reefs of St Gilles, La Saline and St Leu. Mean densities of settlers were higher on reef flats (maximum 474 ind/20 m2 at La Saline) than on back reef areas (maximum 156 ind/20 m2 at La Saline). Seven weeks later, densities of settled E. merra had drastically decreased, and did not differ with site and zone (18.5 ind/20 m2). Percentages of post-settlement mortality at that period ranged from 85 to 88% in back reef areas and from 93 to 95% on reef flats. A strong correlation between density of recruits and per capita mortality suggests density-dependent early post-settlement mortality for E. merra. The limitation of food resources and shelters, perhaps combined with an increase of diseases due to high population densities of settlers, was probably the main cause of mortality just after the mass settlement. Predation by reef fish, including cannibalism between settlers, is probably responsible for most subsequent mortality.

Nitrogen Fixation by Epicaulous Cyanobacteria in the Pointe de la Saline Mangrove Community, Guadeloupe, French West Indies

Nitrogen Fixation by Epicaulous Cyanobacteria in the Pointe de la Saline Mangrove Community, Guadeloupe, French West Indies

Caffeine and the contractility of single muscle fibres from the barnacle Balanus nubilus.

1. In single striated muscle fibres from the barnacle Balanus nubilus tension development following axial injection of caffeine (50 mM in 150 mM-KCl, pH 7.1) was used as an index of releasable Ca. It was shown that fibres incubated in 0 Ca (Na replaced) salines for up to 400 min gave ca. 15% of the control tension response. Inclusion of 1 mM-La in the 0 Ca (Na) saline significantly reversed this decline.2. Estimates of the total fibre calcium assayed under the same experimental conditions indicated a 67% loss of fibre Ca in 0 Ca, and only a 37% loss in La-0 Ca media. No correction was made for the loss of calcium from the extracellular space.3. Experiments with (45)Ca indicated that the efflux of calcium from this preparation was inhibited by 1 mM-La externally and that this effect was still significant even in the presence of 0 Ca (Na) salines. The caffeine-stimulated efflux of Ca was also reduced by ca. 70% in the presence of 1 mM La saline externally.4. The influx and efflux of (14)C caffeine were shown to be rapid, and apparently passive. The diffusion coefficient for caffeine following intracellular injection was 2.4 +/- 0.2 x 10(-6) cm(2) sec(-1) at 18-22 degrees C.5. There was no significant loss of (140)La over a period of 2 hr following axial micro-injection into the fibres.6. In (140)La uptake experiments there was a progressive increase in the La space over 10.5 hr, in contrast to the results with [(3)H]inulin, whose uptake saturated in ca. 1.5 hr. The probability of surface binding and the precipitation of La salts in the extensive extracellular space was suggested as an explanation.7. It is concluded that internal Ca within the sarcoplasmic reticulum, and not cleft or extracellular Ca is the most significant source for these caffeine-induced contractions. Fluxes across the surface membrane can however alter the internal Ca stores over longer periods of time.

The Rocks of La Saline (Northern Jersey)

The rocks of La Saline, an indentation of the larger St. John's Bay, resemble very closely those from Sorel Point, a little less than a mile to the west. Around the latter headland we find that a porphyritic granite has forced its way into a diabase, shattering and breaking it up, softening and locally melting it. Hence changes can be readily traced in the acid magma, which is rendered basic, and in the diabase which is impregnated by it. M. Noury mentions and maps 1 an outcrop of ‘diorite’ at one point in the bay of La Saline and surrounded by granite, but clear evidences of intrusion are wanting. In a quarry on the cliff-top, and cropping out on a sloping path which leads towards the eastern end of the bay, is a rather coarse granite containing some quantity both of hornblende and mica, a fair amount of quartz, and large flesh-coloured orthoclases sometimes ⅘ inch long. At the eastern end, and forming the crags on the shore, occurs a redder rock, less markedly porphyritic and inclining as a rule towards an aplite, though occasionally some quantity of black mica is present; its specific gravity is 2·60. At Sorel Point 2 two distinct intrusions of the acid magma are found: an earlier, porphyritic, which has melted and partly incorporated fragments of the diabase; and a later, non-porphyritic aplite which took the same course as did the first, but without its effect on the diabase. These two have kept