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Macroinfaunal Distribution

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Relationships Among Burrowing Organisms in Mud Flats

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The Lugworm Abarenicola in Bight at the NE Corner of Kalgin Island

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High-Energy Site - South Shoal

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Turbidity and Deposition

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Geomorphic Complexity

Moose Point

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Geomorphic Complexity

Moose Point

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Geomorphic Complexity

Moose Point

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Geomorphic Complexity

Moose Point

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Geomorphic Complexity

Moose Point

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Crustal Deformations from the Great Alaskan Earthquake of 1964

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Eroding Intertidal Platform

Chickaloon Bay

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Sea Level Change Tidal Currents

Wave Action Turbidity

Fluvial Deposition

Erosion Ice Gouging

Sediment Texture

Quiescent Deposition

Organic Concentrations

Larval Survival

Sediment Stability

Migratory Predators

Recruitment Success

BioturbationSedentary Predation

Success of Adult Macro-Infaunal Populations

Primary Factors

Secondary Factors

Tertiary Factors

Primary Biological Effects

Secondary Biological Effects

Ultimate Consequence

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Tectonic Changes in Sea Level

Tidal Currents

Wave Action Turbidity

Fluvial Deposition

Erosion Ice Gouging

Sediment Texture

Quiescent Deposition

Organic Abundance

Larval Survival

Sediment Stability

Migratory Predators

Recruitment Success

BioturbationResident Predation

Success of Adult Macro-Infaunal Populations

Primary Factors

Secondary Factors

Tertiary Factors

Primary Biological Effects

Secondary Biological Effects

Ultimate Consequence

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Factors Influencing Distribution & Abundance of Long-lived Infaunal Organisms

• Two primary factors affecting the distribution of intertidal infauna in Cook Inlet appear to be:

– Extreme tidal currents caused by the large tidal flux and shape of the basin

– Massive loads of silt being dumped from the northern river systems

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Secondary Factors for Infaunal Organisms

• Erosion

• Sediment texture

• Larval survival

• Food availability (organic abundance)

• Predation by adult infauna and migratory predators

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Site Evaluation

WORTHWHILENOT

WORTHWHILE WORTHWHILENOT

WORTHWHILEEAST SIDE OF INLET WEST SIDE OF INLET

Clam Gulch Boulder PointNE Chisik

IslandKalifornsky

Beach Bishop BeachNo. Tuxedni

BayChickaloon Bay Moose Point Polly Creek

No-name CreekBeach

MIDDLE OF INLET Redoubt CreekSE Corner of

Kalgin Is.Shoal South of

Kalgin Is.Harriet Point

NorthOld Cannery

CreekOldmans Bay,

Kalgin Is.Shoal West of

Kalgin Is.West Foreland

SouthNE Kalgin

IslandNW Kalgin

IslandWest Foreland

North

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Conclusions for Sediment and Habitat Conditions

• Range and stability of hydrodynamic conditions in middle and upper Cook Inlet is highly variable

• Wide range of habitats strongly reflects the hydrodynamic and suspended particulate regimes in the inlet

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CONCLUSIONS

• Upper inlet is oligotrophic• Intertidal sediments generally nutrient-poor • Concentrations of TOC and TKN, ranging

from moderate to very low, are inversely correlated with particle grain size and with hydrodynamic energy levels

• Eroding peat may be an important source of nutrition in middle and upper Cook Inlet

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• C:N ratios are inversely correlated with particle grain size and hydrodynamic energy levels

• Based on Carbon:Nitrogen ratios, it is likely that, in locations such as shoals, the major sources of nutrients for infauna may be bacteria living on sediment or detrital particles (or phytoplankton)

Conclusions for Sediment and Habitat Conditions

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If it weren’t for the currents, Cook Inlet would become a gigantic mud flat inhabited with large populations of Macoma balthica

If it weren’t for the mud, Cook Inlet would become current-swept sand and gravel beaches populated with razor or surf clams

Instead, it’s both….

Conclusion

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CONCLUSIONS

• By any measure, it is clear that the sediments contain only very low concentrations of hydrocarbons

• Bivalve populations sampled in upper Cook Inlet have not been exposed to detectable concentrations of petroleum hydrocarbon contaminants

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CONCLUSIONS

• Tissue and surrounding sediment samples consistently produced completely different PAH and AHC profiles

• Mainly naphthalenes represented in tissues

• The limited suite of hydrocarbon analytes in tissue samples indicates that the organisms in upper Cook Inlet accumulate only a subset of all hydrocarbons found in sediments

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Major Factors Likely to Influence Distribution & Abundance of Long-lived Infaunal Organisms

• Intensity of currents and wave action

• Turbidity

• Suspended and deposited nutrition (bacteria, detrital matter, phytoplankton)

• Sediment texture and stability

• Larval settlement and recruitment success

• Mobile and resident predators

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