The Role of Abundant Organic Macroaggregates in Planktonic Metabolism in a Tropical Bay

Abundant large organic aggregates, which form mucous webs up to a few decimeters in length, have been observed in Baía de Todos os Santos (BTS), northeastern Brazil. This communication presents preliminary results from field (February 2015) and laboratory (June 2015) experiments that aimed to determine preliminary values for respiration and near-maximum photosynthesis and the impact of macroaggregates on respiration rates. The experiments included the determination of respiration in controls, with the mechanical removal and addition of macroaggregates. The field experiment during a flood tide presented the lowest respiration rate (−7.0 ± 0.7 µM L−1 d−1), average net primary production (8.9 ± 4.5 µM L−1 d−1), and gross primary production (16.0 ± 10 µM L−1 d−1), with a ratio of gross primary production to respiration of 2.3. The control experiments during an ebb tide showed a mean respiration rate of 8.7 ± 2.3 µM L−1 d−1, whereas, after macroaggregate removal, this was 9.5 ± 4.5 µM L−1 d−1. In the laboratory experiments, the control sample respiration rate of 18.4 ± 1.4 µM L−1 d−1 was slightly increased to 20.6 ± 0.1 µM L−1 d−1 after aggregate removal. The addition of aggregates to the control sample increased the respiration rate by approximately 3-fold, to 56.5 ± 4.8 µM L−1 d−1. These results indicate that macroaggregates could have an important role in pelagic and benthic respiration, as well as in the whole bay’s metabolism.