Epiphytic orchid diversity and community composition in managed and natural moist evergreen Afromontane forest in SW Ethiopia

In SW Ethiopia, the moist evergreen Afromontane forest has become extremely fragmented and most of the remnants are intensively managed for coffee cultivation (Coffea arabica), with considerable impacts on biodiversity and ecosystem functioning. Because epiphytic orchids are potential indicators for forest quality and a proxy for overall forest biodiversity, we assessed the effect of forest management and forest fragmentation on epiphytic orchid diversity. We selected managed forest sites from both large and small forest remnants and compared their epiphytic orchid diversity with the diversity of natural unfragmented forest. We surveyed 339 canopy trees using rope climbing techniques. Orchid richness decreased and community composition changed, from the natural unfragmented forest, over the large managed forest fragments to the small managed forest fragments. This indicates that both forest management and fragmentation contribute to the loss of epiphytic orchids. Both the removal of large canopy trees typical for coffee management, and the occurrence of edge effects accompanying forest fragmentation are likely responsible for species loss and community composition changes. Even though some endangered orchid species persist even in the smallest fragments, large managed forest fragments are better options for the conservation of epiphytic orchids than small managed forests. Our results ultimately show that even though shade coffee cultivation is considered as a close-to-nature practice and is promoted as biodiversity conservation friendly, it cannot compete with the epiphytic orchid conservation benefit generated by unmanaged moist evergreen Afromontane forests.

Abundance and community structures of heterotrophic and oligotrophic bacteria from the Sierra Leone Abbyssal Plain

Colony counts on high and low-nutrient agar media incubated at 2 and 20 °C, Acridine Orange Direct Counts and biomasses are reported for sediments of the Sierra Leone Abyssal Plain. All isolates from low-nutrient agars also grew in nutrient-rich seawater broth (100 % SWB). However, a greater proportion of the 2 °C than of the 20 °C isolates grew in 2.5% SWB, containing 125 mg/l peptone and 25 mg/l yeast extract. Only 14 strains or 12.7% of the 2 °C isolates, but none of the 20 °C isolates, grew in 0.25 % SWB. Psychrophilic bacteria with maximum growth temperatures below 12 °C, isolated at 2 °C, were predominant among the cultivable bacteria from the surface layer. They required seawater for growth and belonged mainly to the Gram-negative genera Alteromonas and Vibrio. In contrast to the earlier view that psychrophily is connected with the Gram-negative cell type, it was found that cold-adapted bacteria of the Gram-positive genus Bacillus predominated in the 4 to 6 cm layer. The 20 °C isolates, however, were mostly Gram-positive, mesophilic, not dependent on seawater for growth, not able to utilize organic substrates at 4 °C, and belonged mainly to the genus Bacillus and to the Gram-positive cocci. The majority of the mesophilic bacilli most likely evolved from dormant spores, but not from actively metabolizing cells. It can be concluded that only the strains isolated at 2 °C can be regarded as indigenous to the deep-sea.

Seawater carbonate chemistry and community calcification during Shiraha coral reef (Ishigaki Island, Japan) studies, 1995

Only about half of all the CO_2 that has been produced by the burning of fossil fuels now remains in the atmosphere. The CO_2 "missing" from the atmosphere is the subject of an important debate. It was thought that the great majority of the missing CO_2 has invaded the ocean, for this system naturally acts as a giant chemical regulator of the atmosphere. Although it is clear that ocean processes have a major role in the regulation of the carbon dioxide content of the atmosphere through air-sea exchange processes, recent studies of the oceanic carbon cycle and air-sea interaction indicate that oceanic carbon is in a quasi-steady state via the system of biological and physical processes in the ocean interior. It is difficult to determine whether the ocean has the capacity to take up the increasing air-born CO_2 released by human activities over the past five or six decades. To understand this enigma, we need a better understanding of the natural variability of the oceanic carbon cycle.

Effects of ocean acidification on population dynamics and community structure of crustose coralline algae

Calcification and growth of crustose coralline algae (CCA) are affected by elevated seawater pCO2 and associated changes in carbonate chemistry. However, the effects of ocean acidification (OA) on population and community-level responses of CCA have barely been investigated. We explored changes in community structure and population dynamics (size structure and reproduction) of CCA in response to OA. Recruited from an experimental flow-through system, CCA settled onto the walls of plastic aquaria and developed under exposure to one of three pCO2 treatments (control [present day, 389±6 ppm CO2], medium [753±11 ppm], and high [1267±19 ppm]). Elevated pCO2 reduced total CCA abundance and affected community structure, in particular the density of the dominant species Pneophyllum sp. and Porolithon onkodes. Meanwhile, the relative abundance of P. onkodes declined from 24% under control CO2 to 8.3% in high CO2 (65% change), while the relative abundance of Pneophyllum sp. remained constant. Population size structure of P. onkodes differed significantly across treatments, with fewer larger individuals under high CO2. In contrast, the population size structure and number of reproductive structures (conceptacles) per crust of Pneophyllum sp. was similar across treatments. The difference in the magnitude of the response of species abundance and population size structure between species may have the potential to induce species composition changes in the future. These results demonstrate that the impacts of OA on key coral reef builders go beyond declines in calcification and growth, and suggest important changes to aspects of population dynamics and community ecology.

Seawater carbonate chemistry and community calcification during a Molokai reef (Hawaii) study 2006

The severity of the impact of elevated atmospheric pCO2 to coral reef ecosystems depends, in part, on how seawater pCO2 affects the balance between calcification and dissolution of carbonate sediments. Presently, there are insufficient published data that relate concentrations of pCO2 and CO3 to in situ rates of reef calcification in natural settings to accurately predict the impact of elevated atmospheric pCO2 on calcification and dissolution processes. Rates of net calcification and dissolution, CO3 concentrations, and pCO2 were measured, in situ, on patch reefs, bare sand, and coral rubble on the Molokai reef flat in Hawaii. Rates of calcification ranged from 0.03 to 2.30 mmol CaCO3 m**-2 h**-1 and dissolution ranged from -0.05 to -3.3 mmol CaCO3 m**-2 h**-1. Calcification and dissolution varied diurnally with net calcification primarily occurring during the day and net dissolution occurring at night. These data were used to calculate threshold values for pCO2 and CO3 at which rates of calcification and dissolution are equivalent. Results indicate that calcification and dissolution are linearly correlated with both CO3 and pCO2. Threshold pCO2 and CO3 values for individual substrate types showed considerable variation. The average pCO2 threshold value for all substrate types was 654±195 µatm and ranged from 467 to 1003 µatm. The average CO3 threshold value was 152±24 µmol/kg, ranging from 113 to 184 µmol/kg. Ambient seawater measurements of pCO2 and CO3 indicate that CO3 and pCO2 threshold values for all substrate types were both exceeded, simultaneously, 13% of the time at present day atmospheric pCO2 concentrations. It is predicted that atmospheric pCO2 will exceed the average pCO2 threshold value for calcification and dissolution on the Molokai reef flat by the year 2100.

Seawater carbonate chemistry and community calcification during Miyako Island (Japan) coral reef studies, 1994

Coral reefs are characterized by enormous carbonate production of the organisms. It is known that rapid calcification is linked to photosynthesis under control of the carbonate equilibrium in seawater. We have established a model simulating the coexisting states of photosynthesis and calcification in order to examine the effects of photosynthesis and calcification on the carbonate system in seawater. Supposing that the rates of photosynthesis and calcification are proportional to concentrations of their inorganic carbon source, the model calculations indicate that three kinds of unique interactions of the organic and inorganic carbon productions are expected. These are photosynthetic enhancement of calcification, calcification which benefits photosynthesis and carbonate dissolution induced by respiration. The first effect appears when the photosynthetic rate is more than approximately 1.2 larger than that of calcification. This effect is caused by the increase of CO3 content and carbonate saturation degree in seawater. If photosynthesis use molecular carbon dioxide, the second effect occurs when the calcification rate is more than approximately 1.6 times larger than that of photosynthesis. Time series model experiments indicate that photosynthesis and calcification potentially enhance each other and that organic and inorganic carbon is produced more efficiently in the coexisting system than in the isolated reactions. These coexisting effects on production enhancement of photosynthesis and calcification are expected to appear not only in the internal pool of organisms but also in a reef environment which is isolated from the outer ocean during low tide. According to the measurements on the fringing type Shiraho Reef in the Ryukyu Islands, the diurnal change of water properties (pH, total alkalinity, total carbon dioxide and carbonate saturation degree) were conspicuous. This environment offers an appropriate condition for the appearance of these coexisting effects. The photosynthetic enhancement of calcification and the respiratory inducement of decalcification were observed during day-time and night-time slack-water periods, respectively. These coexisting effects, especially the photosynthetic enhancement of calcification, appear to play important roles for fluorishing coral reef communities.