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
38
0.8 0.4
37 77 76 Longitude (°W)
0
4 3 2 1 0 10 20 30 40 Depth (m)
0
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
35000
10
7
30ʼ 27ʼ
Copepodites Station: M1 240 238
5 Station: M2 244 242 238 240 12-17 September 2013
242
Station: M3 238 240 244
244
242
4 3
5
2
10 15
1
20
0 Station: M1 256
258
260
Station: M2 256
258 Day
260
Station: M3 256
258
260
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
S2
S1
35ʼ
30ʼ
25ʼ
76°W
30
S3
20ʼ
35 15ʼ
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
0.020
C5 Male Female
Adults combined Female Male
0.015
0.010
15000 Mean concentration of stages of A. tonsa at each station (m-³)
Males
20
21ʼ
20000
6
15
24ʼ
10000 5000 0
12-17 September 2013
35000
C1 C2 C3 C4
30000
C5 Male Female
25000 20000
Vertical Life Table estimate of mortality rate (day-¹)
Females
10
M3
25
25-31 August 2013 C1 C2 C3 C4
M2
M1
25000
0
25
30000
Dissolved O2 (mg L-¹)
Depth (m)
25
Previous project
0 5
Mean Concentration of A. tonsa
8
20
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.
5
15
MOCNESS & CTD Stations
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
33ʼ
N3
N2
Depth (m)
Latitude (°N)
1.2
5
Project Goal: • Determine the relative importance of advective and biological processes on populations of the copepod Acartia tonsa in Chesapeake Bay
N1
38°N
1.6
39
6
Dissolved O2 concentration (mg L-¹)
2.0
Ln [Zooplankton Biovolume (ml m-³ + 1)]
James J. Pierson, Nicholas J. Nidzieko, Michael R. Roman, David E. Elliott, Catherine Fitzgerald
0.005
0
12-17 September 2013
0.020
Adults combined Female Male
0.015
0.010
15000 10000
0.005
5000 0
M1
M2 Station
M3
Mean concentration (m-³ ± standard error) of Acartia tonsa copepodites and adults by stage at each station on each cruise.
0
M1
M2 Station
M3
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