Lecture 14 Estuaries & salt marshes

estuary

a body of water where rivers meet the sea and form an estuary with varying salinity /brackish water and a unique place where only certain adapted orgs can live

blue carbon

term for carbon that gets stored/sequestered like kelp forests sequestering carbon on the ocean floor etc with a super low turnover rate. in theory restoring seagrass beds etc helps sequester more carbon to help combat climate change

salt wedge

a type of estuaries where the river energy is rather high (compared to dense oceanwater ) and there is a sharp ‘wedge’ gradient , distinct layers of salinity, not well mixed, sharp halocline. CB is an example, a ton of river input, big ones like susquehanna and potomac, and tidal forces a lil weaker

stenohaline vs euryhaline

euryhaline better at handling huge range of salinity changes(brackish species), stenohaline is more minimally resistant, prefers high salinity(marine)

osmoregulators vs osmoconformers

osmoconformers ‘conform’ to the water around them. osmoregulators spend energy to regulate their osmotic pressure. most osmoconformers cant handle the brackish environment. this helps explain why low diversity is a thing

osmoconformers don’t have to spend energy on dealing with regulating osmotic pressure BUT it makes them vulnerable to dramatic saline changes

remane curve

curve that shows salinity and species #, lots of fresh in low saline, lots of marine in high saline, and estuarine are in the middle where the others are low. shows that estuarine diversity isn’t really that high, BUt super high production and abundance of what does live there. this is an ecotone (transitional state between ecosystems or communities)

ecotone

transitional zone between communities/ecosystems(ex: estuaries btwn marine and fresh)

nurseries

estuaries are nurseries for several species! esp things like biphasic life cycle organisms like anadromous fish that go home to freshwater to spawn then grow up in the ocean. good things abt estuaries for babies: shelter(seagrass etc) to hide from predators, avoid stenohaline predators , warmer water for rapid growth, also just generally productive habitat

Cordgrass/spartina: spartina patens(salt meadow cordgrass), spartina alterniflora

huge species of seagrass that makes up the salt marsh! has awesome adaptations like salt excretion and aerenchymal tissue to handle salty water. ecosystem engineer! helps with erosion/habitat, creates base for ecosystem. also has clonal rhizome system

aerenchymal tissue

a type of spongy tissue with holes of plants like spartina that allows for gas flow and brings oxygen to things like roots that might be surrounded by anoxic soil. helps them survive flooding and survive intertidal stress

why are estuaries important?

they are super biologically productive, home for tons of different species, store a ton of carbon, nursery for things, help with coastal protection, help filter out pollutants etc

ecosystem services

erosion control, nurseries, flood control, carbon storage, nutrient recycling

estuarine productivity

among highest in world. low diversity, but abundant and productvie!lots of nutrients from river influx, less comp and predators!

SO PROD BC RIVER NUT AND ELSS COMP AND PRED

EStuarine food web

4 primary producers. seagrasses are huge PP, and diatoms/seaweeds , and phytoplankton and mangroves. def bottom up control. detritus is also super important to all of it

estuarine circulation

water can stay in estuaries for a long time! long residence time: CB is 110-260days! seaward flow brings waste and larvae to ocean near surface and denser colder ocean water comes in beneath bringing nutrients and juveniles etc

salinity gradient

marine33-35, polyhaline 30 mesohaline15 , oligohaline5, tidal freshwater 0.5

poly/meso/oligo/tidal fresh/nontidal fresh

salt marsh zonation

depends on salt tolerance! must be able to handle salty flooding by water. mudflats with benthic diatoms, then marsh w spartina alterniflora, spartina patens, thigns like juncus, pickleweed, upland marsh plants, maybe some trees

spartina adaptations

aerenchymal tissue(holes for gas transport), salt excretion, RHIZHOMES clonal spreading quickly. rhizomes penetrate mud and provide oxygen to anoxic muddy dead areas!

spartina fauna helpers

fiddler crabs dig around and aerate soil! mussels contribute some nutrietns via feces, oysters provide structural support, also contrib nutrietns

sesarma trophic cascade new england salt marshes

humans did some serious overfishing! these fish were predators of the crab sesarma, and sesarma grazes on spartina, went crazy and knocked out spartina:(