Download PPT

Zooplankton processes
Puget Sound Oceanography
Jan. 28, 2011
Plankton – “that which is made to wander or drift”
organisms that float or weakly swim through water
Phytoplankton – organisms that use sunlight to fix carbon
Zooplankton – the animal portion of the plankton; herbivorous,
carnivorous, or mixed
Autotrophs – fix their own energy from inorganic substances (producers).
Heterotrophs – depend on energy fixed by others (consumers)
Mixotrophs – do both
Holoplankton – are planktonic through their whole life cycle
Meroplankton – are planktonic only during part (usually larval) stage of their
lives
Herbivores
Carnivores
Omnivores
Characteristics of estuaries:
• Highly advective
• Strong gradients
• Fronts / mixing
• Very productive
• Benthic / pelagic coupling
• High abundances of organisms
• Terrestrial influences
• Human influences
Zooplankton need:
• food
• to avoid predators
• find good growth habitat
• find mates
• ‘life cycle closure’
Special challenges for estuarine species:
• tolerating / responding to strong gradients
•overcoming advection
• predator density
• contaminants / pollution
• altered food webs
Species are zonated along gradients of salinity:
Species composition (meso-zooplankton):
Freshwater
Moderate diversity:
Cladocerans (e.g., Daphnia)
Freshwater molluscs
Typically 5-7 species of copepods
Freshwater jellyfish (rare)
Truly estuarine
a few species of calanoid copepods, usually 1-2 dominant
Meroplankton (bivalves, barnacles, crabs)
jellyfish
Oceanic
high diversity of copepods (>30 spp)
amphipods
euphausiids
jellyfish
meroplankton (echinoderms, bivalves, barnacles, crabs)
Zonation of species distributions along salinity gradients:
Cumulative salinity distribution of
common zooplankton in San
Francisco Bay
E. affinis = Eurytemora (a copepod)
Kimmerer (2004)
Salinity gradients (species patterns set by tolerance) - diversity lowest in brackish
water (5-10‰)
Why??
Species richness in estuaries follows a long
established pattern along the salinity gradient
described by Remane (1934)
Acartia tonsa is only found in
estuaries and nearshore
environments.
H0: they cannot feed
effectively on very low
phytoplankton
concentrations.
(Feeding)
Species gradients also set by behavior:
(Food)
Paffenhoffer et al, 1988
Microzooplankton:
rapid reproduction and growth.
Highly dependent on food and temperature.
At maximum, doubling rates in hours!
Jellyfish:
annual life cycle,
growth to 0.7 d-1
Crustaceans
Copepods
~ 1 month to complete
Egg
Nauplius
(6 stages)
Adult
Copepodites
(5 stages)
Generalized seasonal cycles of phytoplankton and
zooplankton biomass:
Late, single bloom
J
F
M
A
M
J
J
A
S
O
N D
Early, bi-modal bloom
J
F
M
Phytoplankton
Zooplankton
A
M
J
J
A
S
O
N D
Difference of ~1 month between Main Basin and Dabob Bay phytoplankton blooms and
copepod reproduction
Dabob vs. Main Basin
Zooplankton
Dabob vs. Main Basin
Phytoplankton productivity
Percent composition
Calanus marshallae
1st appearance of
young life stages
(purple)
Calanus pacificus
Zooplankton diel vertical migration (DVM):
Who migrates?
Crab larvae
Shrimp
Large copepods
Euphausiids
Some Jellyfish
Some Amphipods
Chaetognaths
Pteropods
Magnitude of Diel Vertical Migration by Life Stage
Life History Stage
0
25
50
Average nighttime depth
Depth (m)
75
100
125
Range of migration
150
175
200
Average daytime depth
Vertical migration in 2-layer circulation
River end
Ocean end
Some may migrate on tidal cycle for transport:
Fernandes et al. 2002
http://northweb.hpl.umces.edu/videos_animations/Oyster_Larvae_Animations.htm
North et al, MEPS 2008
Copepod abundance #/m3
Gelatinous predator predation on zooplankton in Chesapeake Bay
Ctenophore abundance #/m3
Inverse relationship between calanoid copepod and
Mnemiopsis leidyi densities at two stations in Chesapeake
Bay.
Optical Plankton Counter (OPC)
OPC mounted on a
ScanFish