estuaries

definition

- partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with free connection to the open sea

geologic: drowned river valley

- sea level rise

- much wider than deep

- V shaper cross sections

- unobstructed sea connection

geologic: bar built

- mixed zone somewhat separated from sea by sand spits or barrier islands

- = "semi-enclosed"

= sedimentation = high

geologic: fjord (glacial)

pleistocene glaciers deepened existing rivers

- width:depth = small

- steep sides and u shaped cross sections

- mouths = sill (glacial deposits)

geologic: tectonic

- geologic subsidence associated with faults

- san fran bay

less dense water means

inflowing freshwater

salt-wedge estuary

- freshwater flow larger than marine input

- less dense freshwater flows on top and thins as it mixes forming a wedge (depends on flow)

- strong halocline

- mouth = same as river flow

partially mixed estuary

- freshwater flow moderate and moderate tidal influence

- bottom sediments: friction stress and salinity changes

- volume of water flowing out of mouth >> river flow

well mixed estuary

- broad shallow estuary with strong tides

-- no halocline

-- strong horizontal salinity gradient river

-- wide basin means coriolis force significant

negative circulation

- common along arabian gulf

- low FW inputs

- seawater flows in at he surface

- high evap at head of estuary --> hypersaline

estuaries are at the top of

unit value

what are the adaptations for salinity variations

- physiology (osmoregulators and osmoconformers)

- avoidance behavior

- life histories

avoidance behavior

- moves as tides flow

- find less variable habitat in the sediments

- most molluscs able to clam up to avoid suboptimal conditions

life history adaptations

- anadromy (lamprey and salmon, migrate to freshwater to reproduce)

- catadromy (eels, migrate to ocean to reproduce)

property:property plots

- salinity is approximately 'conservative' in estuaries (mixing of freshwater and saltwater)

- net source v net sink

- freshwater --> marine

mixing diagrams

easy way to understand what is happening to a substance as it flows through estuary

ETM (estuarine turbidity maxima)

- common feature

- very fine sediments in rivers hits saltier water --> flocculation

- very light sediments easily disturbed by inflowing seawater

estuary productivity

- most productive natural ecosystems in the world

- due to 3 types of primary producers (phytoplankton, benthic algae, marsh grasses)

- ebb and flow of tides

- nutrients from rivers

- year round productivity

- 2K

what are some energy sources from estuaries

- autochthonous NPP

- allochthonous (DOM and POM)

phytoplankton NPP

- rarely nutrient limited due to rivers and tides

- LIMITED by light and flushing out

benthic algae NPP

- mudflats form in estuaries with large tidal range

- very rich habitat

- birds feed during low tides

most estuaries are heavily dominated by

detrital energy flow

threats to estuaries: human devo

- 7/10 largest cities= on an estuary

- 13% land mass, 40% human pop

threats to estuaries: pollution

- sewage

- shipping centers= industrial centers

- cole matson lab = evolutionary adaptation to pollution

threats to estuaries: non-indigenous species

- transportation centers

- brackish water species can travel better

- brackish water= few species, so higher potential of establishment

threats to estuaries: altered hydrology

dams

- keep seawater out

- no tides= pastures

- pooled water

reduced river flow --> increased salinity