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Based on the pathlines of the flow field of the pelagic copepod Euchaeta rimana, we calculated some characteristics of the velocity gradient field: vorticity, shear, and squared rates of strain. We found that this copepod created a sheared laminar flow field, which is most intense near the moving paired second antennae and transports a volume of water similar to that measured in feeding experiments. The far‐field flow is a combination of first‐order and higher order scanning currents that serve to overcome nega

We analyse drifter data from the Northeast Atlantic and find that single‐particle motion has fractal dimension D = 1.28 ± 0.08 at scales 5 to 100 km. The single particle trajectories are modeled using fractional Brownian motion. Integral time scale is therefore shown to be a function of both the time between position fixes and the length of the total period the drifter was tracked. The variance (particle dispersion) grows as approximately t3/2. The probability density function of single‐particle velocity is observed to be leptokurtic, consistent with the fractional Brownian motion model. The present work reports two‐particle trajectories with fractal dimension D = 1.3 for scales from 8 km to 150 km. The two‐particle dispersion is modelled as accelerated fractional Brownian motion, in which speed becomes a function of time elapsed since the particles were very near to each other. The acceleration is chosen to be consistent with the patch variance growing as t2.34. The dependence of relative velocity between pairs of drifters separated by a distance l, is observed to scale as l0.3. This is consistent with the accelerated fractional Brownian motion model for two‐particle motion.

During a multiyear fish tracking study, subadult and adult life stages of Shubenacadie River striped bass (Morone saxatilis) were detected throughout winter in the well-mixed, hypertidal waters of the Minas Passage, Bay of Fundy. Thirty-five percent of the striped bass tagged with Vemco V16 transmitters were detected by two Minas Passage receiver arrays. Transmissions were received on 82% of winter days (December to April) and by all receivers spanning the width of the passage. Tagged striped bass were detected largely within the top 20–40 m during the day. The extent of vertical migration to shallower waters at night showed a strong relationship with water temperature; however, there was no diel vertical movement pattern observed at water temperatures <1 °C. Our results demonstrate overwintering of a portion of the Shubenacadie River striped bass population in high-flow inner Bay of Fundy waters, which extends the northern limit of this species’ winter marine range. This study is also the first to describe the relationship between daily vertical migration by striped bass and low water temperatures. Both findings suggest an elevated potential risk of interaction with an in-stream tidal turbine facility in Minas Passage.

Drifters are used to measure the structure of an eddy on %restern Bank, Scottan Shelf over a 5 day period. A regression method that uses both the temporal •nd spatiM structure of flow field observations is presented and used to •nalyze this eddy. The eddy h•s vorticity-1.9x10 -s s -• with divergence, stretching deformation and shearing deformation smaller by more than an order of magnitude. The eddy is centered on the crest of Western Bank. The motion residual to the eddy had a slab like part that moved all points on a plane in a circle without rotation. This latter type of motion can cause substantiM error when vorticity and other eddy properties •re estimated using methods titat operate on a single drifter track. The Eulerian statistics of residual motion show correlations greater than 0.5 are restricted to spatial separations less than 2 km and temporal lags less than 3 b, but motion directed along the vector separating two velocity measurements has a significant Eulerian correlation for timescMes of more than 40 hours and length scales of order 5 km. Transverse motion is positively correlated over lesser scales. Much cluster distortion results from subtidal fi-equency motion that has spatial scales that are seldom coherent over drifter separation scales greater than 2-3 km. The long Lagrangian timescale is inconsistent with a description of horizontal mixing in terms of an eddy diffusion coefficient. Rather, we might picture drifters being dispersed by slowly evolving, narrow streams of current that have larger spatial scales Mong their a•s th•n across their axis.

Breakdown and nutrient dynamics of submerged macrophytes were studied in Myall Lake, Australia. Mass loss of Myriophyllum sulsagineum was the lowest (64.90%) among the studied macrophytes during the 322 days followed by charophytes (60.79%), whereas Najas marina and Vallisneria gigantea lost 91.15 and 86.02% of their respective initial mass during that time. The overall exponential breakdown rates of Najas marina and Vallisneria gigantea were similar, with k-values of 0.24 and 0.23 day À1 , respectively. These rates were significantly higher than the break down rates of charophytes (0.007 day À1 ) and M. sulsagineum (0.008 day À1 ). During growth phase, water column depicted lower nutrient concentrations while during decay period, significant increase in water column nutrients resulted. Release of nutrients from decomposing macrophytes and incorporation of these nutrients into sedimentary phase as well as uptake of nutrients by the growing macrophytes, can present a considerable cycling pathway of nutrients in Myall lake system. The results of this study suggest that different submerged macrophytes may differ appreciably in quality and may exhibit different decomposition rates, patterns and nutrient dynamics in aquatic ecosystems in general, and Myall lakes in particular.

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