하구및 연안생태Coastal management 2014 년 가을학기

Estuarine geomorphology and physical oceanography Circulation patterns Stratification Mixing and flushing Time scale; when hydrodynamic changes occur quickly relative to biological, geological and chemical transformations Dominant controlling factors for estuarine ecological processes Organizing of estuary Classification of estuary Physical characteristics of estuary

Galciation cycles LGM; 15,000 yr Current level in 5000 yr Estuaries are common in broader coast line: 80~90% east coast of US; 10~20 % in west coast. During glaciation period, estuaries are rare !! Because sea level is in continental shelf During last 1 My, only 10~20% of the time presented in current conditions current estuaries  filled with sediment  quickly disappear; for geological point of view “extremely short !” In current condition. Takes 9,500 yr to fill up Fill-up didn’t happen, because, sea level rise + erosion of sediment

From lagoons to deltas Geological development of estuary Glaciation cycling Sediment supply Climate variability Regional and local geology Marine energy input; wave + tides Lagoons : marine wave actions; behind barrier island; sand sized sediments; S. Texas Deltas: produced by river processes Protrude into a receiving basin Fine grained silt sediments Estuarine lagoon, estuaries, estuarine deltas ;wave energy + river input combinations

From lagoons to deltas Davis (1973) continuum of estuarine types : from lagoons to delta. Lagoons : marine wave actions; behind barrier island; sand sized sediments; S. Texas Deltas: produced by river processes Protrude into a receiving basin Fine grained silt sediments Estuarine lagoon, estuaries, estuarine deltas ;wave energy + river input combinations

Estuary settings An estuary is a partially enclosed body of water formed where freshwater from rivers and streams flows into the oceans, mixing with the seawater. Although influenced by tides, estuaries are protected from the full force of the ocean waves, winds and storms by reefs, barrier islands or fingers of land, mud, and sand Can be bays, lagoons, harbors, and inlets or sounds.

Estuary definition “estuary” is of sixteenth century origin, derived from the Latin word aestuarium meaning marsh or channel. An estuary is a semienclosed coastal body of water that has free connection with the open sea and within which seawater is measurably diluted with freshwater derived from land drainage (Pritchard 1963). 연안 환경에 속하는 수역으로 강물이 바다로 유입하고 강의 어귀는 만의 형태를 이루어 해수가 조석작용에 의해 혼합 희석됨으로써 광염성 생물 종들이 서식할 수 있는 곳.

Estuary definition Fairbridge (1980) an estuary is an inlet of the sea reaching into a river valley as far as the upper limit of tidal rise, usually being divisible into three sectors: a) a marine or lower estuary, in free connections with the open sea; b) a middle estuary subject to strong salt and freshwater mixing; and c) an upper or fluvial estuary, characterized by freshwater but subject to strong tidal action. The limits between these sectors are variable and subject to constant changes in the river discharges

Pritchard (1963) and Fairbridge (1980) For Pritchard it is the upstream limit of salt penetration for Fairbridge it is the upstream limit of tidal penetration, which in an un-modified estuary will always be further inland.

A new defnition (Day et al.1987) An estuarine system is a coastal indentation that has a restricted connection to the ocean and remains open at least intermittently. tidal river zone mixing zone Near shore turbid zone; between mixing zone and the seaward edge of the tidal plume at full ebb tide  included adjacent coastal waters

Dynamic boundaries Boundaries change position continuously Tidal cycles; spring neap tides Annual cycles Geologic time scale Freshwater discharge some estuaries does nto have all the zones Cancun bay; no tidal river Amazon river; no mixing zone

Water balance (Pritchard, 1952) positive estuaries : evaporation < freshwater Negative estuaries : evaporation > freshwater Neutral : evaporation = freshwater

Water balance (Pritchard, 1952) No loger in common use Most estuaries are positive!!

Geologic classifications(topography) Coastal plain; Drowned river valley; most common. since the last Ice Age, which is within the last 10–15,000 years V shaped cross sections Salt marsh estuaries; lack of a major river; estuary-salt marsh connections; Fjord: Drowned glacial troughs. Fjord-type estuaries occur where valleys have been deeply eroded by glaciation: West of Scotland, Fjords in Norway, Sweden, Alaska, British Columbia, New Zealand, such as the coasts of Norway, Western Scotland, Alaska, and New Zealand. Lagoons; Bar-built: Also drowned river valleys, but recent sedimentation has kept pace with their drowning so that they have a characteristic bar across their mouths, tectonic

Geologic classifications(topography) Lagoons; Bar-built: Also drowned river valleys, but recent sedimentation has kept pace with their drowning so that they have a characteristic bar across their mouths Shallow 1~2 m Physical process; wind dominated

Driving force determining salinity gradient in an estuary The salinity: seawater(35) coastal seas (33) tropical waters (37). salinity of estuarine waters: between 0.5 and 35; brackish, The balance between tide and freshwater determines salinity gradient twice-daily rhythm of the tides. The seawater that enters the estuary is then measurably diluted with freshwater flowing into the estuary from rivers.

Mixing type Highly stratified/Salt wedge: Mississippi (US), N. Esk (UK), Vellar (India) Fjord :Norwegian fjords, West of Scotland sea lochs. Silver Bay (Alaska), Alberni Inlet (British Columbia) Slightly stratified; partially mixed common Vertically mixed: Delaware, Raritan(US), Solway Firth (UK), Mandovi-Zuari (India)

해수의 밀도

salt wedge estuary. Freshwater: surface Middle : entrainment (mixing) occurs and saltwater is mixed into the outflowing freshwater

Fjord estuary Freshwater : surface renewal of tidal water: seasonally or nonrenewal  anoxic

Partially mixed estuary. undiluted freshwater will only be found near the head of the estuary. Coriolis force: more seawater on the left side (northern hemisphere)

Homogeneous estuary in the northern hemisphere. the circulation in homogeneous estuary will be across the estuary from left to right, rather than vertically as in the other types

하구의 분류 (염분과 유속) (저층염분-표층염분)/평균염분 표층의 순 흐름속도/전단면적의 평균 강물 유속

하구의 분류 (조차)

Vegetation microtidal estuaries have only limited intertidal areas, Mesotidal : extensive intertidal areas, covered in vegetation, such as Spartina, macrotidal and hypertidal : bare mudflats without large plants, but with microscopic microphytobenthos.

하구의 염분 특성 염분 (salinity); 해수 1kg 중에 녹아있는 염분의 양. Major elements Trace elements; dissolved gas, nutrients

염의 보존적 특성 Law of relative proportion: Marcet’s law 하구에서는 맞지 않을 수도 있다. 그러나 주요원소는 대부분 보존적 특성을 보인다.

Conservative versus non-conservative Source or sink 의 유무에 따라 Conservative: 강물 유입, 해수혼합, 확산 등 물리적 적용에 의해서만 농도가 변함. Non-conservative;변환, 제거 기작이 있을때; 흡착, 생물에 축적, 흡수, 생성; 생태 환경에 중요.

Classifications

하구의 물질 유입 토사, 중금속, 폐기물, 생화학물질 Dissolved, colloidal, particulate Suspended load versus bed load

Flushing time the time required to replace the existing freshwater in the estuary by the river discharge. total volume of river water accumulated in the estuary (Q) by the/ river flow (R) predicting the impact of polluting discharges on estuaries, short flushing time is generally better mixed and better able to accept effluents.

Flushing velocity Mean annual discharge/area

Estuarine sediments muds are a most characteristic feature of estuaries “a mixing region between sea and inland water of such shape and depth that the net resident time of suspended (sedimentary) materials exceeds the flushing”

흡착과 응집 전기 화학적, 물리화학적, 생물학적 작용 물질의 크기를 크게 하여, 퇴적시키는 효과 광물; 산화철, 산화망간, 탄산칼슘 유기물 표면 면상응집; flocculation Enmeshment: 공기방울이나 침전물에 걸림

면상 응집(flocculation) 작은 입자들이 충돌하여 입자의 크기가 커짐 어느정도 입자의 크기가 커지고 속도가 느려지면, 모두 같은 속도로 이동하여 더 이상의 면상 응집은 일어나지 않는다.

생물학적 퇴적 (bio deposition) 퇴적물 식자에 의한 부유물질 흡수및 배출과정

생물활동에 의한 퇴적 촉진 점액질 미생물 군집에 의해 입자의 크기가 커짐

기타 공기방울 -용존 상태나 콜로이드 상태의 유기탄소 흡착;박테리아서식 광물표면에 용존원소 흡착 철 유기산등이 해수의 이온과 만나 무거워져 침전