Nitrogen and phosphorus uptake rates of different species from a coral reef community after a nutrient pulse.

Terrestrial runoff after heavy rainfall can increase nutrient concentrations in waters overlying coral reefs that otherwise experience low nutrient levels. Field measurements during a runoff event showed a sharp increase in nitrate (75-fold), phosphate (31-fold) and ammonium concentrations (3-fold) in waters overlying a fringing reef at the island of Curaçao (Southern Caribbean). To understand how benthic reef organisms make use of such nutrient pulses, we determined ammonium, nitrate and phosphate uptake rates for one abundant coral species, turf algae, six macroalgal and two benthic cyanobacterial species in a series of laboratory experiments. Nutrient uptake rates differed among benthic functional groups. The filamentous macroalga Cladophora spp., turf algae and the benthic cyanobacterium Lyngbya majuscula had the highest uptake rates per unit biomass, whereas the coral Madracis mirabilis had the lowest. Combining nutrient uptake rates with the standing biomass of each functional group on the reef, we estimated that the ammonium and phosphate delivered during runoff events is mostly taken up by turf algae and the two macroalgae Lobophora variegata and Dictyota pulchella. Our results support the often proposed, but rarely tested, assumption that turf algae and opportunistic macroalgae primarily benefit from episodic inputs of nutrients to coral reefs.

Rare Moss-Built Microterraces in a High-Altitude, Acid Mine Drainage-Polluted Stream (Cordillera Negra, Peru).

The Rio Santiago in the Cordillera Negra of Peru is severely contaminated by acid mine drainage in its headwaters. In a strongly acid stream, at about 3800 m above sea level (masl), microterraces were found with terrace walls built up of dead moss, with encrustations and interstitial fine, creamy sediment. The stream water was turbid due to the presence of similar suspended sediment, which also occurred as a thin basal layer in inter-rim basins. The moss was identified as the rare bryophyte Anomobryum prostratum (Müll. Hal.) Besch. Chemical and mineralogical analyses show that green, living parts of the moss are gradually coated by Al/Fe (hydr)oxides, inducing their senescence and death. The necromass is covered by creamy crusts through precipitation of schwertmannite-type material from the stream water and simultaneous 'capture' of fine sediment. The latter consists of a mixture of precipitate and fine detrital primary minerals. These processes are held responsible for the formation of the microterraces, which regarding their composition and environment seem to be unique. Remarkable is the high As content of the creamy crusts and sediment, attributed to strong sorption of As, whereas its solute concentration is relatively low. This calls for more attention to suspended fine sediment in the assessment of environmental risks of stream water use. Lastly, the results raise serious doubts about the use of aquatic bryophytes as bioindicator for chemical pollution in acid mine drainage-polluted streams.

Metal specific partitioning in a parasite-host assemblage of the cestode Ligula intestinalis and the cyprinid fish Rastrineobola argentea.

When evaluating metal accumulation patterns in parasite-host assemblages species specific metal requirements should be taken into account. The aim of the present study was therefore to determine the metal specific partitioning in a parasite-host assemblage of the cestode Ligula intestinalis and the cyprinid fish Rastrineobola argentea and to determine the effect of the parasites on the metal balance of the fish. To this purpose the host-parasite assemblage was analysed for several metals at sites in the coastal zone of Lake Victoria differing in metal contamination. Our results showed that some elements (Ca, Sr, and Mg) reflected the physiological differences of bone formation and ionic balance and pointed to physiological disturbances of infested R. argentea. Other essential metals including Cu and Co were subject of element competition between fish and parasite, while only a micro-element (Cr) and a non-essential metal (Cd) displayed a partitioning with high concentration in the parasite. The present study clearly demonstrated the impact of the large cestodes on their small fish hosts and it is concluded that the partitioning of metals in the assemblage of R. argentea and L. intestinalis is subject to metal specific mechanisms for essential and non-essential elements.