Primary productivity

Primary productivity

The synthesis of organic materials from inorganic substances by photosynthesis or chemosynthesis, often autotrophs, able to produce their own food from energy and inorganic molecules

Phototroph

Light energy

Chemotroph

Non light source, chemical source

Lithotroph

inorganic electron source

organotroph

organic electron source

Autotroph

CO2

Heterotroph

organic C

Photosynthesis

Energy from light used to split H20 (light reaction) and reduce carbon from CO2 (with RUBISCO in calvin cycle)

How much of marine primary productivity is based on photosynthesis

>95%

Rubisco

The enzyme that fixes CO2 into organic carbon, the most abundant and important enzyme on earth

Chemosynthesise

convert carbon dioxide into organic matter using the oxidation of inorganic compounds as a source of energy

Spiny lobsters obtain …

20% of their diet from chemosynthetic food sources

Units of primary productivity

C/m2/yr

Phytoplankton provide how much primary productivity

90%

Blue planet

open ocean makes up 93% of the oceans surface, productivity per given area is very small, accounts for around 50% of global estimate, moderates the global environment

Coastal seas

90% of our fish comes from 7% of the ocean, estimated to account for 25% of marine productivity

Sensitive margin between the land and the ocean

Run off from land, Dump site, accessible for fishing, degraded

Key factors controlling the rate and extent of primary production

light and nutrients

Liebigs law of the minimum

The nutrient available in the smallest quantity with respect to the requirements of the plant will limit its growth

Euphotic zone

section of the ocean where primary production occurs, the depth at which 1% of surface light remains, enough for positive growth and productivity when respiration is accounted for, about 200m in the clearest waters

Light in Coastal waters

Blue light absorbed, green reflected, much shallower euphotic zone

light

Light is the primary limiting factor for photosynthesis and as a result primary productivity, The vast majority of the ocean is too dark for photosynthesis, Coastal seas have much shallower photic zone than offshore oceanic water

Major nutrients

Carbon, Nitrogen, Phosphorus, Silicon

Micronutrient

Iron

Nitrate concentration in the ocean

higher conc. in winter when colder, nutrient rich waters are closer to the surface, nitrate limitation can occur in summer, major limiting nutrient in coastal waters

Silicate

Limits growth of diatoms and is often depleted after blooms

Primary productivity

Creation of organic materials from inorganic substances

important nutrients that can limit primary productivity

Nitrogen, phosphorous, silica, iron

nutrient cycling

nutrients recycled through organic matter

Stratification

little mixing between warm surface waters and cool deeper waters, can trap nutrients in deeper waters

What are algae

Eukaryotic, members of the kingdom Protista, are not plants, do not have a vascular system

Monophyletic groups

fungi, animals and higher plants all traced to a single ancestor

Paraphyletic groups of organisms

Diverged at different times and do not have a common ancestor

Defining characteristics of Algae

Flagella at some stage of the life cycle, Reproduce by spores, no roots, mostly photosynthetic, mostly marine

how algae are classified

Photosynthetic pigments, characteristics of flagella, cell wall material, structure

Chlorophyta

Green algae, ancestors of the kingdom plantae, chlorophyll b, cellulose cell wall

Phaeophyta

Brown algae, diatoms and brown seaweeds, filamentous to complicated kelp species, cell wall of alginate, fucoxanthin

Rhodophyta

Red algae, oldest and most diverse algal groups, absence of flagella on spores and gametes, phycoerythrin, phycocyanin, cell wall contains agar and carrageenan

Dinophyta

Dinoflagellates, single celled phytoplankton with flagella

Haptophyta

Coccolithophores, calcifying organisms

Diatoms

major coastal and open ocean phytoplankton, silica cell wall or frustule, accessory pigments fucoxanthin

Centrales

areole arranged in a radial pattern

Pennales

Areole bilaterally symmetrical along a longitudinal axis

Frustule reproduction

valves of frustule separate, new valve grows within the old one, reach about ¼ of the original size and sink, sexual reproduction produces auxospore, full sized cell

carbon export case study

Add limiting nutrient to ocean to promote algae growth, in this case Iron (Fe), Algae grow and fix CO2 through photosynthesis, Algae sink to the deep sea, taking carbon with them

Benthic diatoms

Motile, migrate to surface during low tide

Coccolithophores

Calcite platelets form exoskeletons, asexual and sexual phases can survive in lower nutrient waters compared to diatoms, can be found in rock record and reconstruct past climate

Dinoflagellates

thecal plates secreted within an outer cell membrane, posterior and transverse flagella

Dinofllagellate cysts

resistant stage which stays in sediment until conditions are right, cyst forms inside thecal plates

Harmful algal blooms

low mixing, high nutrients, warm temperatures and high light, Toxic and non toxic harmful algal blooms

Macroalgae or seaweed

Vast majorities are photosynthetic, key primary producers in coastal seas

Why are algae important

Major primary producers, bottom of the food web, habitats for animals, food, Toxic algal blooms, food and products

Marine angiosperms

Vascular plants, have specialized tissue that transports nutrients and water, reproduce with flowers and seeds, seagrasses

what is a kelp forest

Physically formed by brown macroalgae of the order Laminariales, kelp forests provide a unique 3D habitat and are a source of understanding many ecological processes

Why are kelp forests of the ocean

Provide 3D habitat, refuge from predators, important nursery grounds, macroalgae beds can trap larvae, provide surfaces for attachment of larvae/spores

Why good habitats for marine organisms

Less competition for attachment, projection above benthic boundary layer, proved food, DOM and POM

Kelp forests alter flow

Entrain larvae, alter the chemical environment, increased sedimentation, reduce coastal erosion

Autogenic ecosystem engineers

transform ecosystems by their own growth and are integral to the altered environment, corals and kelp forests

Allogenic engineers

Alter the environment and then move on, leaving structures behind. Beavers building dams to block stream flow

Sedimentation

Shading, scouring, burial, can strongly impact macroalgae survival

Key stressors to kelp forests

reduced light for photosynthesis, sedimentation, invasive species, pollution and nutrient run off from land, climate change (durvilieae and macrocystis)

Why is macrocystis pyrifera important

Finifish habitats, cultural, fisheries, transports carbon to coast, abalone food, settlement of crayfish larvae

Local example of kelp forest restoration

Undaria control by Ngāi Tahu

What is a microbes

organisms smaller than 0.1mm or 100 microns, make up an unseen world, affect the visible world

Why does size matter in microbes

SA:V is an index of metabolic rate, SA:V is inversely proportional to linear size,

What is different about microbes

phylogenetic relationships, structure/shape, antibiotic resistance, primary nutritional mode, life history characteristics, growth strategy, motility

Prokaryotes vs Eukaryotes

lack of membrane bound nucleus, smaller ribosomes

Obligate

Required

Facultative

Optional/discretionary

Protists

important consumers of other microbes, either obligate or facultative heterotrophs

Viruses

20-200 nm, important in remineralization of inorganic nutrients, responsible for the viral shunt

Why study marine microbes

Microbes cause disease, provides examples of early life on earth and life on other planets, good model systems for general ecological principles, mediate biogeochemical processes that effect climate, primary producers, account for huge amounts of biomass and very abundant

Microbes causing diseases

Control populations of macroscopic plants and animals, lamprey redding syndrome

What are food webs

Geographical representation that depicts how energy/biomass flows through a ecosystem

Microbial view of marine food webs

phytoplankton fix C during photosynthesis, convert inorgancis C and nutrients into organic matter via photsynthesis, consumed by zooplankton grazers

POM

Particular organic matter, bodies, or fragments of dead organisms as well as fecal material

DOM

Dissolved organic matter, low molecular weight compounds dissolved in seawater

How is detritus formed

Exudation by primary producers, excretion by heterotrophs, slopy grazing, viral lysis

POM to DOM conversion

Via excretion of extracellular enzymes by bacteria, DOM is not readily available to the non-microbial parts of food webs

Microbial loop

Heterotrophic bacteria consume organic carbon released by primary producers and Respire, Remineralise inorganic nutrients, Convert it into biomass

Remineralisation

Releases of inorganic or mineral nutrients and carbon, following decomposition

Microbial carbon pump

Sinking of POM to the ocean floor (marine snow), Recycling of DOM by heterotrophic bacteria transforms labile (usable) DOM to a recalcitrant (unusable) DOM, Leads to long term C storage

What is the viral shunt

Production of DOM by viral lysis and subsequent reutilisation by other microbes, releases entire cellular contents, producing DOM

What is marine snow

Sinking of particulate organic matter to the deep ocean, important for fertilization

Limits to microbial production

Growth rates are lower in nature compared to lab

Biotic top down control of microbes

Predation, viral lysis, competition

Abiotic bottom up control of microbes

Temperature, organic carbon, inorganic nutrients

Labile DOM

Readily degradable DOM that is quickly utilised by microbes

Recalcitrant DOM

DOM that resists microbial degradation and persists for long periods

Predation vs viral lysis

10-50% of bacterial mortality attributed to viruses rest by grazing, viruses important in high nutrient areas, contribute more when protists do not grow well

Microbial grazer

Comsume its prey and oxidize organic carbon to CO2

Microbial viral lysis

Releases the entire cellular contents, producing DOM

Seasonal patterns driven by microbes

early spring, increase in photosynthesis followed by respiration, late spring decreases, summer slight increase, winter, and autumn regeneration