Turbidity and Deposition Geomorphic Complexity

Turbidity and Deposition

Geomorphic Complexity

Geomorphic Complexity

Geomorphic Complexity

Geomorphic Complexity

Geomorphic Complexity

Eroding Intertidal Platform

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

Secondary Factors for Infaunal Organisms

• Erosion

• Sediment texture

• Larval survival

• Food availability (organic abundance)

• Predation by adult infauna and migratory predators

Site Evaluation

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

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

Conclusions for Sediment and Habitat Conditions

• 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)

Conclusion

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

CONCLUSIONS

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

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