Or
Export of Secondary Production in Ecosystems
BECAUSE MOST OF THE
PRODUCTIVITY AND
ENERGY IS IN
PLANTS & VERY
LITTLE IS IN
ANIMALS,
ANIMALS CAN’T BE
IMPORTANT IN
STRUCTURING
ECOSYSTEMS.
RIGHT?
TWO ROLES OF ANIMALS
Transformation
Translocation
Kitchell et al. 1979
BioScience 29: 28 -34
WHY MIGHT TRANSLOCATION BE
CONSUMERS IMPORTANT?
• Mobility and behavior of animals can cause
substantial and rapid redistribution of nutrients.
• They can readily cross physical mixing
boundaries, such as temperature or salinity
stratification.
• They often make migrations that cross ecosystem
boundaries.
• They are TASTY bits that enter foodwebs
MENHADEN
ESTUARY
ECOSYSTEM
BOUNDARY
JUVENILE
0-age year class
LARVAE
1, 2, 3 age year class
EGGS
OCEAN
ADULT
MASS BALANCE
The mass of how many larvae entering the estuary equals the
mass of one juvenile leaving the estuary?
Entering
Leaving
NET EXPORT IS A FUNCTION OF:
GROWTH RATE
Increase in size
of individual
TIME
MORTALITY RATE
How many are there?
TIMING OF
MIGRATION
When do they cross the
ecosystem boundary
compared to growth and
mortality?
TIME (OR SIZE)
GROWTH AND TIMING
LEAVING
ENTERING LEAVING
Timing
February
October
22
90
Dry Weight (g)
0.02
4.4
Nitrogen (ppt)
120
117
Phosp. (ppt)
26
30
Length (mm)
ENTERING
MASS BALANCE
Break even number is the number of larvae entering that exactly balance one juvenile
leaving = Net flux of zero
Net Flux = exit-enter
-
(# juv. exit) x (mass one juv. )*(ConcJuv)
(# larvae enter) x (mass one larvae)*(ConcLarvae)
Net Flux = Zero
0 = (1 juvenile) x (mass)*(C ) J
(? larvae) x (mass)*(CL)
? Larvae = (1 juvenile) x (mass)x (CJ) / (mass)*(CL)
Breakeven # =
(
)
x (% NJ)
/(
)
x (% NJ)
LEAVING
Areal net flux
(g /m2/ yr)
Menhaden
Detritus
(water-borne)
Carbon
23
150
Nitrogen
3
4
Phosphorus
1
1
ENTERING
EXPORT FROM ESTUARIES
TO OFFSHORE ECOSYSTEM
Areal net flux
(g /m2/ yr)
Menhaden
Detritus
(water-borne)
Carbon
23
150
Nitrogen
3
4
Phosphorus
1
1
An Ecosystem Subsidy
Big Bend Seagrass
3000 km2 of seagrass
High primary production
Exports:
Lots and Lots of Pinfish
Seagrass
Offshore Reefs
Northeastern Gulf of Mexico
Lower primary production
High fishery yields
Leave and most do not return
Louisiana Oil Industry
Florida Seagrass Value
Florida Beach Tourism
The State of Florida has more than 11,000 km2 of seagrass.
The Florida Big Bend contains >3,000 km2 of seagrass, the largest
continuous span in the state.
Brr…
Let’s get
out of
here.
SEAGRASS
Shallow/Deep
Reefs
GAG
13C 25 % (S.E. 0.63)
 34S 18.5 % (S.E. 0.01)
Benthic Feeders
Piscivores
Pinfish Abundance
2009
2010
Apalachicola River
Atmosphere
Trichodesmium
Nitrogen Sources
Apalachicola River
1.7*1010 g N yr-1
Atmospheric Deposition
5.4*1010 g N yr-1
Big Bend Pinfish
6.5*108 N yr-1
Trophic steps required to become available to gag
3-4
3-4
Tropic transfer efficiency of Nitrogen = 0.28
Apalachicola River
1.3*109–3.8*108 g N yr-1
Atmospheric Deposition
1.2*109-3.3*108 g N yr-1
0
Big Bend Pinfish
6.5*108 N yr-1
Based on our estimates a single species of fish (Pinfish) flux ~14-36 % of the total
nitrogen available to grouper annually in the N.E. Gulf of Mexico. Since the pinfish
flux is directly available as a prey item and is not lost to bacterial respiration or
sedimentation we hypothesize that this flux contributes significantly to the high
fishery yields in the area.
Nitrogen Sources
Apalachicola River
1.7*1010 g N yr-1
Atmospheric Deposition
5.4*1010 g N yr-1
Big Bend Pinfish
6.5*108 N yr-1
Trophic steps required to become available to gag
3-4
3-4
Tropic transfer efficiency of Nitrogen = 0.28
Apalachicola River
1.3*109–3.8*108 g N yr-1
Atmospheric Deposition
1.2*109-3.3*108 g N yr-1
0
Big Bend Pinfish
6.5*108 N yr-1
Based on our estimates a single species of fish (Pinfish) flux ~14-36 % of the total
nitrogen available to grouper annually in the N.E. Gulf of Mexico. Since the pinfish
flux is directly available as a prey item and is not lost to bacterial respiration or
sedimentation we hypothesize that this flux contributes significantly to the high
fishery yields in the area.
In our system seagrass habitat and the productive inshore
environment provide a significant source of organic matter to the
offshore environment via the movement of fishes.
This link is critical to the reproduction of a highly valuable fisheries
species in the northern Gulf.
These fishes also carry organic toxins such as MeHg and thus
provide a link between near shore pollution and contamination of
food fishes (e.g. grouper and tuna).
Globally this phenomenon is likely very common in temperate coast
regions where season changes in temperature make near shore
waters too cold to inhabit.
Stable isotopes provide a powerful tool than can be used to quantify
the impacts of ecosystem subsidies.
The TIDE project
Trophic cascades and Interacting control processes in a Detritusbased aquatic Ecosystem
The TIDE project is a National Science
Foundation Integrated Research
Challenges in Environmental Biology
(IRC-EB) funded study investigating the
long-term fate of coastal marshes in the
Plum Island watershed. Specifically this
project will look at the interactive effects
of nutrient enrichment and the removal of
top level consumers in several small tidal
creeks of the Rowley river.
Consequences in Ecosystems
Johnson & Short 2012
Pair-wise Regression
R2=0.99, p= 0.004
Trophic Bottleneck
Observed an increase (4x) in the abundance
of inedible long lived snails in fertilized
creek.
Mummichog experience high mortality over
the winter.
Increased direct or indirect competition for
food between the long lived snail and the
short lived mummichog.
Control Conditions
Eutrophic Condition Short Term
Effects on Fisheries Species?
Eutrophic Condition Long Term
Conclusions
Eutrophication initially increased production of
mummichog but some tipping point was reached and
now production is decreasing
Possible mechanisms are habitat degradation or a
trophic bottleneck. We are working to examine these
new questions.
Mummichog may provide an important trophic
subsidy to striped bass.