The effects of CO2 and nutrient fertilisation on the growth and temperature response of the mangrove Avicennia germinans

In order to understand plant responses to both the widespread phenomenon of increased nutrient inputs to coastal zones and the concurrent rise in atmospheric CO2 concentrations, CO2-nutrient interactions need to be considered. In addition to its potential stimulating effect on photosynthesis and growth, elevated CO2 affects the temperature response of photosynthesis. The scarcity of experiments testing how elevated CO2 affects the temperature response of tropical trees hinders our ability to model future primary productivity. In a glasshouse study, we examined the effects of elevated CO2 (800\ua0ppm) and nutrient availability on seedlings of the widespread mangrove Avicennia germinans. We assessed photosynthetic performance, the temperature response of photosynthesis, seedling growth and biomass allocation. We found large synergistic gains in both growth (42\ua0%) and photosynthesis (115\ua0%) when seedlings grown under elevated CO2 were supplied with elevated nutrient concentrations relative to their ambient growing conditions. Growth was significantly enhanced under elevated CO2 only under high-nutrient conditions, mainly in above-ground tissues. Under low-nutrient conditions and elevated CO2, root volume was more than double that of seedlings grown under ambient CO2 levels. Elevated CO2 significantly increased the temperature optimum for photosynthesis by ca. 4\ua0°C. Rising CO2 concentrations are likely to have a significant positive effect on the growth rate of A. germinans over the next century, especially in areas where nutrient availability is high

Ichthyofauna of the rocky coastal littoral of the Israeli Mediterranean, with reference to the paucity of Red Sea (Lessepsian) migrants in this habitat

The ichthyofauna of the shallow rocky habitats was studied at three different localities on Israel's Mediterranean coast, at three sites, Mikhmoret (45 kin north of Tel Aviv), Habonim (60 km north of Tel Aviv) and Rosh HaNiqra (Israel-Lebanese border). In total, 8387 individuals belonging to 79 species and 31 families were collected, including 35 species that were site attached, 23 resident species and 21 visitor species. The cluster analysis showed no significant differences between the three sites. The Euclidean distance was highest when all species were included, but dropped sharply when visitor species were omitted; the difference value was lowest when only benthic, site-attached species were considered. Seven Lessepsian (Suez Canal) migrant species were among the collected visitor species, two were among the residents, and there were none among the site-attached fish. We suggest that the low mobility and demersal spawning habits of the site-attached Red Sea species could hinder their invasion of the Mediterranean, as no continuous rocky habitat connects the northern Gulf of Suez, the Suez Canal and the southern Mediterranean coast of Israel. In addition, the re-colonization process following defaunation was examined. Monitoring of the study sites following the ichthyocide collections was possible in some cases and indicated that fish re-colonization was a fairly rapid process, complete after approximately 12 months, indicating that while single, small size defaunations can provide valuable information on the fish assemblage, they do not appear to cause long-term damage to such habitats

Near-bottom depletion of zooplankton over coral reefs: III: vertical gradient of predation pressure

Many diurnal planktivorous fish in coral reefs efficiently consume zooplankton drifting in the overlying water column. Our survey, carried out at two coral reefs in the Red Sea, showed that most of the diurnal planktivorous fish foraged near the bottom, close to the shelters from piscivores. The planktivorous fish were order of magnitude more abundant near