Marine Zoology and Ecosystems: Primary Production

Primary production definition

base of marine food web- photosynthesis, rate of organic carbon formation

Sunlight -> producers -> consumers

Marine primary producers

phytoplankton & macroalgae/marine angiosperms

Gross Primary Production (GPP)

total rate of CO2 fixation via photosynthesis

Autotropic Respiration (Ra)

carbon used by producers for metabolic maintenance

Net Primary Production (NPP)

GPP-Ra (what is left for growth, export, higher trophic levels)

New/Export production

portion of NPP that is exported out of the euphotic zones, not respired on surface

Net Ecosystem Production (NEP)

if including respiration by heterotrophs

Seaweed: Marine macroalgae

large, multicellular protists

not true plants

Seaweed: main groups

Green, Brown & red

Green seaweed

Chlorophyta: chlorophyll a & b

shallow waters

Brown seaweed

Phaeophyta: fucoxanthin pigment

cooler waters, kelps

Red seaweed

Rhodophyta: phycoerythrin pigment

deeper waters

Seaweed: Form & Function

blades- analogous function to leaves

pneumatocyst- buoyancy

stipe- flexible to reduce breakage

holdfast- anchors, no roots, no nutrients

Seaweed: Ecology & Zonation

temp defines global distribution patterns

competition and herbivory structure the community

light, wave action, desiccation gradients

Seaweed Productivity

kelp forest 200-1700g C m-2 yr-1

does not get stored long-term

enters food webs as: detritus, dissolved organic matter, consumed by grazers

Seagrass

angiosperms- adapted to full marine life

~60 spp

Seagrass: adaptations

flexible leaves, thin cuticle

hydrophilic pollen- travels in water to different locations

root/rhizome system in sediments

low-light adapted- usually require clear water so they can have light, but usually live with lots of turbidity

seagrass anatomy

Seagrass: Productivity

538g C m-2 yr-1

high carbon burial in anoxic sediments → blue carbon sink

traps sediments= improves clarity

crucial nurseries for fish/invertebrates

Mangroves

flowering trees/shrubs in intertidal tropics

adapted to salinity & anoxia

Mangroves: salinity adaptation

salt excretion- (avicennia), salt exclusion (Rhizophora)

Mangroves: anoxia adaptation

aerial roots (prop roots, pneumatophores)

Mangroves: ecology and ecosystem functions

detrital export supports estuarine & coastal food webs

coastal protection

provide nursery grounds for juvenile fish/shrimp

major long-term carbon sinks (anoxic sediments)

most productive forest in the world

Comparing Coastal producers: Type

Seaweeds- protists

seagrasses- flowering plants

mangroves- trees/shrubs

Comparing Coastal producers: Substrate

seaweeds- hard rocks

seagrass- soft sediments

mangroves- intertidal mud

Comparing Coastal producers: productivity

seaweed & mangroves- high

seagrass- moderate

Comparing Coastal producers: Carbon storage

Seaweed- low

seagrass- medium

mangroves- high

Human impacts: losses

seagrass: 110km2 per year ~7% per year since 1990

mangroves: 0.21% to 0/04%

seaweeds: ~1.8% per year, Kelp 90% loss on hotspots

Human impacts: threats

development, eutrophication, trawling, climate change

Human impacts: conservation

Marine protected areas (MPA), water quality regulation, restoration, blue-carbon credits