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Adaptive feeding is a strategy used by many organisms to maintain growth and reproduction success while encountering varying feeding conditions. Oysters are sessile benthic and non‐siphon filter feeders. Oysters are well adapted to modify the ambient microenvironment through their pumping behavior and particle selection activity. Rejection of unsuitable food particulates bound in pseudofeces via ejection events are an integral part of oyster feeding during which oysters produced strong flow opposite to their inhalant feeding flow. The strong opposite pulsatile flow during the ejection event inevitably disrupts the oyster's normal feeding cycle, but how oysters restart their feeding and allocate their energy consumption during an ejection event has not been investigated. The present study used particle image velocimetry (PIV) to examine the impact of ejection events on the feeding of the American oyster, Crassostrea virginica. The strong pulsatile flow resulting from pseudofecal ejection altered the external flow fields by moving water away from the shell. The initial feeding zone after pseudofecal ejection was relatively narrow, possessed a low pulsatile flow, and did not exploit the full flow field. The feeding zone gradually expanded as the pulsatile flow weakened. The strong shear rate at the stable feeding zone then sustained the feeding flow that facilitated oyster feeding. Furthermore, the volumetric fluxes often increased after the ejection event, suggesting increase in feeding efficiency after ejection events. These PIV studies provide new insight on the interactions between feeding oysters and the surrounding physical environment at small yet ecologically relevant scales. [ABSTRACT FROM AUTHOR]

Plankton are excellent indicators of ecosystem status and fisheries because of their pivotal role in marine food webs and their core values in the integrated ecosystem assessment (IEA). Monitoring plankton is essential to understand their dynamics and underlying processes. Recent advances in imaging technologies have enabled in situ, high-frequency, real-time observations of plankton in coastal waters. While high-frequency plankton time series have provided unprecedented fundamental information about physical and biological processes, understanding and identifying the underlying mechanisms that influence plankton dynamic remains a major challenge. We use high-frequency plankton data from PlanktonScope as an example to examine the impacts of physical and biological processes on plankton dynamics at different temporal scales. Frequency patterns were identified for both environmental factors and different plankton groups that matched in time. Using logistic regression models on the selected daily peaks for different plankton groups, we found that diurnal cycle, monsoon season, and major episodic events, such as typhoons, had major impacts on the dynamics of plankton, as proxied by our indicators. We further synthesized, across multiple spatiotemporal scales in the study area, the impacts of various processes on plankton with different mobility. Our study demonstrates that the suite of plankton indicators simultaneously generated from PlanktonScope provides a robust holistic view of pelagic ecosystem status over a broad range of spatiotemporal scales. In situ imaging systems like PlanktonScope are promising tools for near real-time plankton monitoring and a deep understanding of plankton dynamics. • Plankton imaging systems can generate a suite of near real-time high-frequency plankton indictors. • High-frequency plankton indicators provide an excellent holistic view of ecosystem status and fisheries. • A combination of highfrequency data and frequency analysis revealed the impact of physical processes at different scales. • A trait-based approach allows a comparison among different plankton groups and their response to physical processes. • Automated deep learning approach can reduce the time lag between observations and data availability. [ABSTRACT FROM AUTHOR]

• An in-situ imaging system captured Noctiluca bloom in Dapeng Bay, P.R. China. • A logistic growth model was applied to simulate the growth and decay of Noctiluca. • We demonstrated an early warning framework using the in-situ observations and model. The frequency and intensity of harmful algal blooms (HABs) are likely to increase with climate change and increases in nutrients due to anthropogenic activities. To manage the environment and health threats to surrounding organisms, it is essential to improve our capability to provide early warning of harmful species. Using Noctiluca scintillans as example, a dinoflagellate that often blooms in Asia and whose presence is rapidly expanding worldwide, we demonstrate a potential way to predict N. scintillans blooms by deploying an in-situ plankton imaging system: PlanktonScope. PlanktonScope is a shadowgraph imaging system and capable of imaging organisms 40 µm – 5 cm. This system was deployed in Shenzhen Bay, China, recording images at 0.5 Hz in April 2016. Using the automated image processing procedure, we found that PlanktonScope recorded nearly a full cycle of a N. scintillans bloom. A simple resource-limited logistic population growth model was then applied to develop a predictive framework for the outburst of N. scintillans. Environmental changes could explain the observed dynamics of N. scintillans ; however, it was difficult to quantify the relationship between the dynamics of N. scintillans and environmental variables. Our study demonstrated that a camera system like PlanktonScope could be useful in developing an early warning system for N. scintillans blooms, which could be applicable to other HAB species for proactive management. [ABSTRACT FROM AUTHOR]

Phosphorus speciation in the sediments is regulated by a series of physicochemical and microbial processes, and directly affects water phosphorus pool. However, the influence of culture activities and microbial metabolism on the sedimentary phosphorus speciation is poorly studied. In this study, we compared the abundance of distinguishable phosphorus phases and other physicochemical properties of sediments from oyster-farming areas and reference areas. The Geochip 5.0 technique was introduced to reveal the microbiological mechanisms of phosphorus metabolic alteration. The results showed that oyster culture enhanced the bioavailability of phosphorus in sediments. The free organic phosphorus was reduced significantly, whereas the free inorganic phosphorus and iron-bound phosphorus greatly increased in the oyster culture area (P ≤ 0.05). Moreover, the results of Geochip showed that the oyster culture reshaped the microbial network structure in sediments, with typical phosphate-solubilizing and phosphorus-accumulating microbes being enriched by 17.76% and 10.60%. The abundance of functional genes related to the main phosphorus cycle pathways were also significantly increased (P ≤ 0.05) in the culture area compared to the reference area. This work suggested that oyster culture can greatly improve the microbial phosphorus metabolism and provided insights into the environmental recovery and reconstruction from marine aquaculture activities. [Display omitted] • Biodeposition of oyster shaped a more oxidized sediment environment. • Oyster farming increased the bioavailability of phosphorus in sediments. • Oyster culture enriched the P-cycling microorganisms in sediments. • Sedimentary microbial P-cycle pathways were improved by oyster farming. [ABSTRACT FROM AUTHOR]

[Display omitted] • The nutrient budget in Shenzhen Bay was analysed using the LOICZ model. • Sediment contributed greatly to the eutrophication of Shenzhen Bay. • Sediment resuspension ratios in Shenzhen Bay were 95.45%–99.44%. As a highly eutrophic area, Shenzhen Bay in southern China has accumulated plant dissolved inorganic nitrogen (DIN) and phosphate (PO 4 3--P), resulting in various environmental problems. The nutrient loading was calculated to classify runoff patterns of the bay and provide possible management solutions. However, previous studies have shown that external loading alone cannot explain the source of nutrition in Shenzhen Bay. In our study, for the first time, we proved quantitatively that internal nutrient loading was the main contributor of the total input fluxes of dissolved DIN and PO 4 3--P in Shenzhen Bay using the LOICZ (land–ocean interactions in the coastal zone) model. Our results showed that the internal loading supplied 65 and 69% of total input fluxes of dissolved DIN and PO 4 3--P, which were c. 4.0 × 106 and 0.3 × 106 mol/d, respectively. The estimated nutrient input flux from terrigenous loading were c. 1.38 × 106 and 0.1 × 106 mol/d of DIN and PO 4 3--P, respectively. Notably, the internal loading from sediment resuspension supplied c. 3.5–15.7 × 106 and 0.5–1.9 × 106 mol/d of particle nitrogen and bioavailable phosphate to Shenzhen Bay, respectively. Moreover, 51 and 62% of DIN and PO 4 3--P were exported through water exchange and residual flows from Shenzhen Bay into the Pearl River. These results demonstrate that internal loading dynamics and nutrient losses to the Pearl River jointly influence the eutrophication process in Shenzhen Bay. [ABSTRACT FROM AUTHOR]