OrExport of Secondary Production in

Ecosystems

ECOSYSTEM SUBSIDY EXAMPLES

Salmon returning from the sea

Migrations of birds and large mammals

River movement of detritus

*But very few studies have attempted to quantify the impact of the subsidy in the recipient ecosystem.

BECAUSE MOST OF THE PRODUCTIVITY

AND ENERGY IS IN PLANTS & VERY

LITTLE IS IN ANIMALS,

ANIMALS CAN’T BE IMPORTANT IN STRUCTURING ECOSYSTEMS.

RIGHT?

Kitchell et al. 1979BioScience 29: 28 -34

Transformation Translocation

TWO ROLES OF ANIMALS

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

EGGS

LARVAE

JUVENILE

ADULT

ESTUARY

0-age year class

1, 2, 3 age year class

OCEAN

ECOSYSTEM BOUNDARY

MENHADEN

MASS BALANCEThe 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:

TIMING OF MIGRATIONWhen do they cross the ecosystem boundary compared to growth and mortality?

GROWTH RATEIncrease in size of individual

TIME

MORTALITY RATEHow many are there?

TIME (OR SIZE)

ENTERING

LEAVING

ENTERING LEAVINGTiming February October

Length (mm) 22 90

Dry Weight (g) 0.02 4.4

Nitrogen (ppt) 120 117

Phosp. (ppt) 26 30

GROWTH AND TIMING

MASS BALANCE

Net Flux = exit-enter

(# juv. exit) x (mass one juv. )*(ConcJuv) - (# larvae enter) x (mass one larvae)*(ConcLarvae)

0 = (1 juvenile) x (mass)*(CJ) - (? larvae) x (mass)*(CL)

Break even number is the number of larvae entering that exactly balance one juvenile leaving = Net flux of zero

? Larvae = (1 juvenile) x (mass)x (CJ) / (mass)*(CL)

Net Flux = Zero

/Breakeven # = ( ) ( )x (% NJ) x (% NJ)

ENTERING

LEAVING

Areal net flux

(g /m2/ yr)

Menhaden Detritus (water-borne)

Carbon 23 150

Nitrogen 3 4

Phosphorus 1 1

Areal net flux(g /m2/ yr)

Menhaden Detritus(water-borne)

Carbon 23 150

Nitrogen 3 4

Phosphorus 1 1

EXPORT FROM ESTUARIES TO OFFSHORE ECOSYSTEM

Seagrass

Offshore Reefs

Big Bend Seagrass

3000 km2 of seagrass

High primary production

Exports:Lots and Lots of Pinfish

Leave and most do not return

Northeastern Gulf of Mexico

Lower primary production

High fishery yields

An Ecosystem Subsidy

1. The fall egress of seagrass dwelling fishes to offshore reefs constitutes a major food source for reef communities.

2. This migration contributes directly the reproductive productivity of spring spawning groupers.

THE HYPOTHESIS

SECONDARY PRODUCTION

SEAGRASSShallow/Deep

ReefsGAG

d13C 25 % (S.E. 0.63)d 34S 18.5 % (S.E. 0.01)

Benthic Feeders Piscivores

1. Seagrass habitat derived organic matter reaches shallow water reefs and is consumed by resident species and gag grouper

2. Flux by fin provides ~20 % of the biomass on shallow water reefs and in gag muscle tissue.

3. Gag are likely making a pre-spawning migration to shallow water to feed intensively on the seagrass species.

CONCLUSIONS

DOES FIN FLUX STACK UPPinfish AbundanceNitrogen is the limiting nutrient

in the Gulf of Mexico. This fish flux could represent a large movement of nitrogen to the Gulf.

Lucky for me Chris Stallings of the FSUMCL decided to figure out how many fish are in the Big Bend.

Each year 1.5 Billion pinfish leave the seagrass beds of the Big Bend

By using a length weight curve we can estimate the total amount of organic nitrogen contained in the pinfish flux.

2009 2010

MAJOR NITROGEN SOURCES

Trichodesmium

Apalachicola River

Atmosphere

Nitrogen Sources

Apalachicola River1.7*1010 g N yr-1

Atmospheric Deposition5.4*1010 g N yr-1

Big Bend Pinfish6.5*108 N yr-1

Trophic steps required to become available to gag3-4 3-4 0

Tropic transfer efficiency of Nitrogen = 0.28

Apalachicola River 1.3*109–3.8*108 g N yr-1

Atmospheric Deposition1.2*109-3.3*108 g N yr-1

Big Bend Pinfish6.5*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 River1.7*1010 g N yr-1

Atmospheric Deposition5.4*1010 g N yr-1

Big Bend Pinfish6.5*108 N yr-1

Trophic steps required to become available to gag3-4 3-4 0

Tropic transfer efficiency of Nitrogen = 0.28

Apalachicola River 1.3*109–3.8*108 g N yr-1

Atmospheric Deposition1.2*109-3.3*108 g N yr-1

Big Bend Pinfish6.5*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.

SO WHAT DOES IT ALL MEANIn 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 projectTrophic cascades and Interacting control processes in a

Detritus-based 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 RegressionR2=0.99, p= 0.004

Trophic BottleneckObserved 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

ConclusionsEutrophication 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.