Pierson Ocean Science 2014 Poster V3

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Feb 26, 2014 - Project Goal: • Determine the relative importance of advective and biological processes on populations
Copepods in the Dead Zone:

The roles of behavior and physics in controlling copepod population dynamics in hypoxic systems

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Historical data† shows fewer copepods in the central, mesohaline portion of the Chesapeake Bay in summer, simultaneously with strong hypoxia. Is this directly or indirectly related to the hypoxic conditions?

25-31 August 2013

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Copepodites Station: M1 240 238

5 Station: M2 244 242 238 240 12-17 September 2013

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Vertical distribution over time of Acartia tonsa copepodites, females, and males from each station on each cruise. Bubbles are scaled to concentration (m-³) and centered on the mid-point of layer that was sampled by the MOCNESS. Upper panels from August cruise, lower panels from September Cruise. From left to right panels show stations M1, M2, & M3.

Average DO was lower in August, and oxycline was shallower. Very little hypoxia was found on the shoals. Little evidence of diel vertical migration (DVM) for any stages. Few of any stages are found in hypoxic water. † Figures adapted from: Zhang et al. 2006, Journal of Geophysical Research vol. 111, http://dx.doi.org/10.1029/2005JC003085 Roman et al. 2005, Limnology and Oceanography, vol. 52, http://dx.doi.org/10.4319/lo.2005.50.2.0480 ‡ For more information on the mooring array, please see: The role of wind in estuarine circulation Boicourt, W. C.; Scully, M. E.; Li, M.; Sanford, L. P.; Friedrichs, C. T. Abstract ID: 16012 Session #:074 Wednesday 2/26/2014 09:30 Location: 319 AB This work was supported by NSF OCE grant 1259691 Web: Email: Twitter:

http://hpl.umces.edu/~jpierson [email protected] @planktoneer

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Methods: • Two Cruises in mesohaline Chesapeake Bay, August and September 2013 • Nine stations sampled, M-line presented here • Repeated CTD casts and MOCNESS tows at each station

Mortality Rate of A. tonsa 25-31 August 2013

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12-17 September 2013

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Vertical Life Table estimate of mortality rate (day-¹)

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Mean Concentration of A. tonsa

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ADCP locations‡

2) Vertical migration behaviors of copepods in hypoxic waters change with differing wind and current conditions, to allow the copepods to maintain position in the mesohaline portion estuary.

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Hypotheses 1) Copepods on the lateral flanks of the bay periodically resupply the center portion of the bay

Hypoxic Conditions and Vertical Distribution of Acartia tonsa 0

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Project Goal: • Determine the relative importance of advective and biological processes on populations of the copepod Acartia tonsa in Chesapeake Bay

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Dissolved O2 concentration (mg L-¹)

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James J. Pierson, Nicholas J. Nidzieko, Michael R. Roman, David E. Elliott, Catherine Fitzgerald

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Mean concentration (m-³ ± standard error) of Acartia tonsa copepodites and adults by stage at each station on each cruise.

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Mortality rates (day-¹ ± standard error) of Acartia tonsa adults (calculated as total adults, females, and males) from each station on each cruise.

Acartia tonsa concentrations were higher at flank stations relative to the channel station in the middle.

Male mortality is higher than female mortality at each station and on each cruise.

Overall there are more males than females.

Is this a result of risk-averse behavior by females?

So what can we conclude so far?

What’s next?

• More A. tonsa found on the flanks than in the channel Resupply from flanks is possible Advective loss due to reduced habitat possible

• Complete sample analysis • Estimate exchange between flanks and channel • Update A. tonsa life history model to account for observed advective flux

• Male mortality higher than female for A. tonsa