Abundance of plankton in the upper 200 m layer in tropical oligotrophic regions of the Pacific and Indian Oceans

Quantitative distribution of plankton (mostly mesoplankton) is studied in the upper 200 m layer of oligotrophic waters in tropical anticyclonic gyres of the Pacific and Indian Oceans. Some general features of its trophic and taxonomic structures and vertical distribution are described.

Cacao trees in tropical agroforestry landscapes of the Napu Valley in Central Sulawesi, Indonesia

All sample sites were situated at the northern tip of Napu Valley in Central Sulawesi, Indonesia. After an initial mapping of the study area, we selected 15 smallholder cacao plantations as sites for bird and bat exclosure experiments in March 2010. On each study site, we established 4 treatments for these exclosure experiments (bird exclosure - closed during daytime and open during night; bat exclosure - closed overnight and opened during daytime; full exclosure of both birds and bats - always closed and unmanipulated/open control treatments - always open). In each treatment, there were 2 cacao trees (total of 8 cacao trees per study site), surrounded by nylon filament (2x2 cm mesh size) that was opened and closed according to the activity period of day and night active flying vertebrates (05:00-06:00 am and 17:00-18:00 pm) on a daily basis. The mean tree height and diameter at breast height (dbh) result from two measures of all study trees at the beginning of the exclosure experiment (June 2010) and 6 months later (February 2011).

Avian species identity and predation success in tropical cacao agroforestry of the Napu Valley in Central Sulawesi, Indonesia

Avian ecosystem services such as the suppression of pests are considered being of high ecological and economic importance in a range of ecosystems, especially in tropical agroforestry. But how bird predation success is related to the diversity and composition of the bird community, as well as local and landscape factors, is poorly understood. The author quantified arthropod predation in relation to the identity and diversity of insectivorous birds, using experimental exposure of artificial, caterpillar-like prey on smallholder cacao agroforestry systems, differing in local shade management and distance to primary forest. The bird community was assessed using both mist netting (targeting on active understory insectivores) and point count (higher completeness of species inventories) sampling. The study was conducted in a land use dominated area in Central Sulawesi, Indonesia, adjacent to the Lore Lindu National Park. We selected 15 smallholder cacao plantations as sites for bird and bat exclosure experiments in March 2010. Until July 2011, we recorded several data in this study area, including the bird community data, cacao tree data and bird predation experiments that are presented here. We found that avian predation success can be driven by single and abundant insectivorous species, rather than by overall bird species richness. Forest proximity was important for enhancing the density of this key species, but did also promote bird species richness. The availability of local shade trees had no effects on the local bird community or avian predation success. Our findings are both of economical as well as ecological interest because the conservation of nearby forest remnants will likely benefit human needs and biodiversity conservation alike.

Bird observation and sampling in tropical agroforestry landscapes of the Napu Valley in Central Sulawesi, Indonesia

We investigated the local bird community in Central Sulawesi (Indonesia), with focus on insectivorous species in the agroforestry landscapes adjacent to the Lore Lindu National Park. All study sites were situated at the northern tip of Napu Valley in Central Sulawesi, Indonesia. After an initial mapping of the study area, we selected 15 smallholder cacao plantations as sites for our study in March 2010. These sides were mainly used for bird and bat exclosure experiments. All sited were situated along a local gradient (shade availability on each plantation) and a landscape gradient (distance to primary forest), which were independent from each other. In September 2010 and from February until June 2011, we assessed the bird community on our 15 study sites using monthly point count and mist netting sampling. Point count (20 minutes between 07 am and 10 am and in between the net checking hours) and mist netting surveys (12 hours, between 05:30 am and 17:30 pm) were conducted simultaneously but only once per month on each study site, to avoid habituation of the local bird community to our surveys. Further, point counts were conducted at least 100 m apart from the mist netting sites, to avoid potential disturbance between the two methods. We discarded all observations beyond 50 m (including those individuals that flew over the canopy) from the statistical analysis, as well as recaptures of individuals within identical mist netting rounds.

Biogeochemical investigation of cold seep sediments in the Eastern Mediterranean Sea

Cold seep ecosystems are highly productive, fragmented ecosystems of the deep-sea floor. They form worldwide where methane reaches the surface seafloor, and are characterized by rich chemosynthetic communities fueled by the microbial utilization of hydrocarbons. Here we investigated with in situ (benthic chamber, microprofiler) and ex situ (pore water constituents, turnover rates of sulfate and methane, prokaryote abundance) techniques reduced sites from three different seep ecosystems in the Eastern Mediterranean deep-sea. At all three cold seep systems, the Amon Mud Volcano, Amsterdam Mud Volcano and the Nile Deep Sea Fan Pockmark area, we observed and sampled patches of highly reduced, methane-seeping sulfidic sediments which were separated by tens to hundreds of (kilo)meters with non-reduced oxygenated seafloor areas. All investigated seep sites were characterized by gassy, sulfidic sediments of blackish color, of which some were overgrown with thiotrophic bacterial mats. Fluxes of methane and oxygen, as well as sulfate reduction rates varied between the different sites.

Biomass and substrate utilization of cold adapted bacteria in Fram Strait and the Western Greenlad Sea

During the 'Polarstern' expedition ARK-IV/2 in June 1987, water samples from 8 stations were taken to study biomass and substrate utilization of cold adapted bacteria. Bacterial biomasses determined from acridine orange direct counts (AODC) were between 0.4 and 31.4 µ/g C/l, and ATP concentrations amounted from <0.1 to 40 ng/l. Colony counts on seawater agar reached only 0.1% of AODC, but with the MPN-method 1 to 10% of AODC were recorded. With 14C-glutamic acid or 14C-glucose as tracer substrate in oligotrophic broth containing 0.5 mg trypticase and 0.05 mg yeast extract per liter of seawater, obligately oligotrophic bacteria could be detected in one water sample. Although incubation was at 2 °C, only psychrotrophic bacteria showing growth temperatures between 1 and 30 °C were obtained. Organic substrate utilizations by 106 isolates were tested at 4 and 20 °C. Most carbohydrates, organic acids, alcohols, and alanine were assimilated at both temperatures, but arginine, aspartate and ornithine were utilized only at 20 °C by almost all strains.

Contrasting effects of ocean acidification on reproduction in reef fishes

Differences in the sensitivity of marine species to ocean acidification will influence the structure of marine communities in the future. Reproduction is critical for individual and population success, yet is energetically expensive and could be adversely affected by rising CO2 levels in the ocean. We investigated the effects of projected future CO2 levels on reproductive output of two species of coral reef damselfish, Amphiprion percula and Acanthochromis polyacanthus. Adult breeding pairs were maintained at current-day control (446 µatm), moderate (652 µatm) or high CO2 (912 µatm) for a 9-month period that included the summer breeding season. The elevated CO2 treatments were consistent with CO2 levels projected by 2100 under moderate (RCP6) and high (RCP8) emission scenarios. Reproductive output increased in A. percula, with 45-75 % more egg clutches produced and a 47-56 % increase in the number of eggs per clutch in the two elevated CO2 treatments. In contrast, reproductive output decreased at high CO2 in Ac. polyacanthus, with approximately one-third as many clutches produced compared with controls. Egg survival was not affected by CO2 for A. percula, but was greater in elevated CO2 for Ac. polyacanthus. Hatching success was also greater for Ac. polyacanthus at elevated CO2, but there was no effect of CO2 treatments on offspring size. Despite the variation in reproductive output, body condition of adults did not differ between control and CO2 treatments in either species. Our results demonstrate different effects of high CO2 on fish reproduction, even among species within the same family. A greater understanding of the variation in effects of ocean acidification on reproductive performance is required to predict the consequences for future populations of marine organisms.

Calcification is not the Achilles'heel of cold-water corals in an acidifying ocean

Ocean acidification is thought to be a major threat to coral reefs: laboratory evidence and CO2 seep research has shown adverse effects on many coral species, although a few are resilient. There are concerns that cold-water corals are even more vulnerable as they live in areas where aragonite saturation (Omega ara) is lower than in the tropics and is falling rapidly due to CO2 emissions. Here, we provide laboratory evidence that net (gross calcification minus dissolution) and gross calcification rates of three common cold-water corals, Caryophyllia smithii, Dendrophyllia cornigera, and Desmophyllum dianthus, are not affected by pCO2 levels expected for 2100 (pCO2 1058 µatm, Omega ara 1.29), and nor are the rates of skeletal dissolution in D. dianthus. We transplanted D. dianthus to 350 m depth (pHT 8.02; pCO2 448 µatm, Omega ara 2.58) and to a 3 m depth CO2 seep in oligotrophic waters (pHT 7.35; pCO2 2879 µatm, Omega ara 0.76) and found that the transplants calcified at the same rates regardless of the pCO2 confirming their resilience to acidification, but at significantly lower rates than corals that were fed in aquaria. Our combination of field and laboratory evidence suggests that ocean acidification will not disrupt cold-water coral calcification although falling aragonite levels may affect other organismal physiological and/or reef community processes.

Macroinvertebrate abundance in tropical Andean streams, Ecuador

Deforestation in the tropical Andes is affecting ecological conditions of streams, and determination of how much forest should be retained is a pressing task for conservation, restoration and management strategies. We calculated and analyzed eight benthic metrics (structural, compositional and water quality indices) and a physical-chemical composite index with gradients of vegetation cover to assess the effects of deforestation on macroinvertebrate communities and water quality of 23 streams in southern Ecuadorian Andes. Using a geographical information system (GIS), we quantified vegetation cover at three spatial scales: the entire catchment, the riparian buffer of 30 m width extending the entire stream length, and the local scale defined for a stream reach of 100 m in length and similar buffer width. Macroinvertebrate and water quality metrics had the strongest relationships with vegetation cover at catchment and riparian scales, while vegetation cover did not show any association with the macroinvertebrate metrics at local scale. At catchment scale, the water quality metrics indicate that ecological condition of Andean streams is good when vegetation cover is over 70%. Further, macroinvertebrate community assemblages were more diverse and related in catchments largely covered by native vegetation (>70%). Overall, our results suggest that retaining an important quantity of native vegetation cover within the catchments and a linkage between headwater and riparian forests help to maintain and improve stream biodiversity and water quality in Andean streams affected by deforestation. Also, this research proposes that a strong regulation focused to the management of riparian buffers can be successful when decision making is addressed to conservation/restoration of Andean catchments.

Bird predation experiments in tropical agroforestry landscapes of the Napu Valley in Central Sulawesi, Indonesia

We performed bird predation experiments (dummy experiments), using artificial prey and bird community data to investigate the importance of predator diversity vs. predator identity in cacao agroforestry landscapes. All sample sites were situated at the northern tip of Napu Valley in Central Sulawesi, Indonesia. After an initial mapping of the study area, we selected 15 smallholder cacao plantations as sites for our exclosure experiments in March 2010. For our predation experiment, we selected 10 (out of 15) study sites and 5 cacao trees per site for the application of artificial prey for birds (dummy caterpillars made of plasticine). Our study trees (numbered from 1 to 5 per site) were randomly chosen and we kept spacing of at least two unmanipulated cacao trees between two study trees to avoid clumped distribution. To quantify both daytime/diurnal predation and night-time/nocturnal predation (e.g. birds vs. bats), we applied 7 caterpillar dummies on all study trees and controlled them for predation marks in the early morning (05:00-06:00 am), in the evening (17:00-18:00 pm) and in the early morning on the next day (completing one survey round). In total, we performed four survey rounds per study site (in June and July 2011). The caterpillar dummies were always applied in the same order and on three different parts of each cacao study tree: One 'control dummy' (located on first branching of the cacao tree); 3 'branch dummies' (located on one main branch coming from first branching; 20-25 cm between single dummies) and 3 'leaf dummies' (3 medium aged cacao trees adjacent to main branch were selected and single dummies placed in the center of each cacao leaf). The different positions were chosen to control for different foraging modes of predators (e.g. branch gleaners versus leaf gleaners). During day- and nighttime surveys, we controlled if the dummy caterpillars were still present in their original position, if they were absent and could not be relocated on the ground or if they were fallen to the ground, but could still be recorded. Eaten dummies were counted as 1 mark usually, except for those dummies, where two or more different kind of arthropods had eaten parts of the dummy (2 marks or more). Other predation marks were added to this number. For each dummy, we counted the total number of different predation marks. We focused on predation marks that could be identified with certainty (based on preliminary observations and/or literature): marks of birds, rodents and snails. Finally, we analysed the relationship of bird predation marks and bird community parameters (abundance vs. diversity), as well as effects of local and landscape management on the avian predation success.

Rates of nitrogen cycling and chemo-autotrophy in the cold-water coral Lophelia pertusa

Cold-water corals (CWC) are widely distributed around the world forming extensive reefs at par with tropical coral reefs. They are hotspots of biodiversity and organic matter processing in the world's deep oceans. Living in the dark they lack photosynthetic symbionts and are therefore considered to depend entirely on the limited flux of organic resources from the surface ocean. While symbiotic relations in tropical corals are known to be key to their survival in oligotrophic conditions, the full metabolic capacity of CWC has yet to be revealed. Here we report isotope tracer evidence for efficient nitrogen recycling, including nitrogen assimilation, regeneration, nitrification and denitrification. Moreover, we also discovered chemoautotrophy and nitrogen fixation in CWC and transfer of fixed nitrogen and inorganic carbon into bulk coral tissue and tissue compounds (fatty acids and amino acids). This unrecognized yet versatile metabolic machinery of CWC conserves precious limiting resources and provides access to new nitrogen and organic carbon resources that may be essential for CWC to survive in the resource-depleted dark ocean.