Marine Ecology: Ecosystem Ecology

What is a salt marsh

What is a salt marsh

salt-tolerant herbaceous plants/small shrubs that live in sedimentary shorelines. Protected from waves and flooded/drained by tides

What are two other major vegetated coastal wetland habitats?

Seagrasses and mangroves

What is the latitudinal distribution of saltmarshes

Middle to high latitudes (temperate to boreal)

Low energy coasts (brown)

(ACE) Alaska, Canada, England

How did the origin of salt marsh and other plant-based foundation species habitats impact the ecological dynamics observed in those habitats?

Areas with a lot of primary succession plants were thought to be controlled by bottom-up forces (nutrients, tides, physical factors) with little effect of top-down (predation) forces.

Found later that plant competition and herbivory (crabs) had a large effect on zonation in these areas (top-down effects)

Main physical stressor in salt marshes

salinity stress

Saltwater evaporates=increase in salt levels=salty sad plants

What physical and biological environmental factors drive salt marsh community structures

Depends on area… but mainly

lower limits set by physical stress (waterlogged soil, anoxia) and upper limits set by competition (plant zones)

What is a foundation species

Species that create habitats and modify environments with positive effects on diversity, distribution and abundance of associated organisms

Name all foundation species in marine ecosystems

Reef-building corals, kelp, seagrasses, saltmarsh cordgrass, mangroves, oysters, hydrothermal vent tubeworms, sponges in Antarctica

What habitat/community were foundation species first described from

Sponges in Antarctica

How does the presence of a foundation species alter community structure/dynamics

can provide substrate as well as reduce biotic and abiotic stress and increase the food supply in area

results in higher diversity, abundance and biomass, wider distribution limits, and elevated rates of propagule retention, settlement and survivorship

Large and broad net positive effect on community structure

Describe the facilitation between Juncus grass species and Iva marsh elder species that illustrates a shift between competition and facilitation with environmental gradients in New England salt marshes

Juncus shades the soil surface and decreases salt build up
Low-marsh level plants aerate oxygen-poor soil and this benefits neighbor plants (Juncus aerates, Iva benefits. Iva pushes seaward) Juncus is weaker than Iva and is displaced closer to sea

What are seagrass habitats

highly productive ecosystems that are a nursery for many species, stabilize sediment, filter water, and recycle nutrients

What do seagrass habitats require to thrive

Where are seagrass habitats found?

Temperate and tropical seas+ freshwater communities

Describe how seagrass habitats have a positive effect on nearby coral reefs/mangrove habitats

seagrasses buffer coral reefs from terrigenous influence

binds sediment, absorbs nutrients, matures fish, filters bad bacteria

Coral reefs buffer waves/currents and export fish & nutrients

What were the main patterns/can you describe the figures in the study of the impact of run-off/untreated waste in islands across Indonesia where there are seagrass beds between the shoreline and the reefs versus areas where there are no seagrass beds?

decreases in amounts of bacteria in both the area between the shore and the reef and the reef in areas where seagrass is present.

What is the role of herbivory in seagrass habitats

Roles between big herbivores and small is unclear as well as the role of herbivores themselves

What is the mutualistic grazer model

A shift in the hypotheses for the major drivers of seagrass communities (thought to be bottom-up, but this model says perhaps top-down)

Grazers of algae and grazers of the seagrasses both increase the survivability of the seagrass ecosystem?? 4-level trophic facilitation vs 2 level

How does the mutualistic grazer model keep algae from dominating seagrass habitats

Dominance of seagrass as opposed to algae is influenced by grazing

Small crustaceans/gastropods reduce overgrowth of seagrasses by eating algae

Describe how a trophic cascade might work in seagrass habitats

Less top predator=more intermediate predator fish=crash in crustacean mesograzers= more algae= algae outcompetes seagrasses

Number of strong interactions is low so trophic cascade chances are higher

Describe two potentially stable states in seagrass communities and their factors

Feedback mechanisms reinforce states

Sea-grass dominated (high seagrass biomass= low efficiency of small predators, high abundance of mesograzers, low algal biomass)

Algae-dominated (low seagrass biomass, high small predator efficency, low abundance of mesograzers, high-algal biomass)

Facilitation

interactions between 2+ species where one species (at least) benefits and nobody is negatively affected

Can result from ecosystem engineering

Ecosystem engineers

modify physical habitat and provide whole-community facilitation

Foundation species

This “model” describes how seagrass beds provide shelter from predators for herbivorous species that then prevent microalgae from overgrowing and outcompeting the seagrass:

Mutualistic grazer model

How do dynamics of hydrothermal vents differ from other deep sea habitats? (enviromental parameters, gradients, types of species, nutreint levels, ecological drivers, habitat comp) ??????

Deep sea: Stable physical environment, mostly soft sediment, no light, low water temp, high pressure, constant salinity, slow currents, hella oxygen, low food

Primary producers of hydrothermal vents (via chemosynthetic microbial processes)

bacteria and archaea fix inorganic carbon into organic matter

free-living bacteria, endosymbionts, ectosymbionts

Environment of hydrothermal vents

rich in hydrogen sulfide, manganese, iron, methane, hydrogen, and toxic metals. Steep chemical and thermal gradients, high local biomass, no oxygen

How does most deep-sea biomass and diversity relate to latitudinal gradients, and what is driving this pattern?

Regions with higher primary production support more deep-sea benthos & high latitude regions have higher biomass

Driven by surface primary production

How/why do hydrothermal vent communities not follow latitudinal patterns for deep-sea biomass/diversity

They dont correlate with high surface productivity, they are associated with mid-ocean ridges

Distribution of hydrothermal vent communities

mid-ocean ridges, volcanic arcs and back arcs, hot spot volcanos all can form hydrothermal vents

What information led scientists to hypothesize the existence of hydrothermal vents before getting “eyes” on them in the mid-1970s?

heat fluxes, high manganese concentrations, low magnesium concentrations

Why was the discovery of hydrothermal vents mindblowing at the time

Everyone believed that primary producers required light then they found primary producers that didnt need light

Different species form the “foundation species” around different hydrothermal vents – but what are the commonalities among these species in terms of their adaptations to these environments?

High temperature adaptation, novel photoreceptors (cant form images), fast-growing with high metabolisms

Siboglinid tubeworms, vesicomyid clams, bathymodiolid mussels, alvinocard shrimp, pompeii worm

What are the other species typically found around hydrothermal vents and what are the most common functional groups they fit into?

Mobile predators and scavengers: galatheid crab, brachyuran crabs, vent fish, vent octopus

Sessile suspension feeders: anthozoans, enteropneusts, serpulid polychaetes, barnacles

Are there large, mobile, top predators in hydrothermal vent communities

….kinda

There are vent fish and octopuses as well as crabs

What are the gradients in temperature, oxygen, toxic metals, hydrogen sulfide from the core vent plumes moving out?

Temp gets colder, oxygen gets higher, toxic metals gets lower, H2S gets lower

Given the distribution of vents in the deep sea, how does larval dispersal work in connecting these vent communities?

Rapid colonization and population growth suggest long-distance dispersal, migrate along mid-ocean ridges

Is there ocean basin-scale connectivity in deep-sea vents? Is each vent its own community of species?

vent fauna differs between oceans

How does the biomass of kelp forests change seasonally

Highest in winter (more nutrients, cold water)

Lowest in late summer/fall (low nutrients, warm water)

How do El Nino conditions affect kelp forests in California, and what is the specific cause and effect relationship(s)?

Higher abundance because upwellings=colder water=more nutrients

What are the major predators of sea urchins? How does this vary geographically

Codfish, wolf eel, crabs, sea otters, starfish, sheephead fish, lobsters

Why are sea otters considered keystone species in Alaska but considered to have less impact in California?

In California, sea urchins are also eaten by lobster and sheep head fish while in Alaska their main predator is sea otters.

Lower biomass of sea otters in California.

How do sea otters affect the biomass and depth distribution of kelp

they indirectly increase their biomass and allow more growth in the first 20m of water

Key limiting nutrient for kelp forests

nitrate

The majority of kelp forest productivity is…

exported to other habitats (kelp wrack) and eaten by deposit feeders

Photosymbiosis is a common strategy for organisms in the many tropical habitats but uncommon or absent in temperate and polar habitats. Explain the primary reason for this absence?

Colder waters have more nutrients present while warmer waters are nutrient-limited. Nutrients arent limited in the water, so nobody needs to create more yk

In general, how do coral growth rates change with depth and why?

no reef-building corals deep, but corals still grow

no light, so coral has to find other methods of energy accumulation. Harder/slower growth

How do growth morphologies of coral change with wave stress?

Higher wave energy=low-lying corals and algae less vulnerable to physical stress

Lower wave energy= upright and structurally complex corals

What are the main environmental factors driving growth forms in coral?

wave energy, seawater temperature, and primary production???

What is the (broad) latitudinal distribution of coral reefs?

For tropical, shallow-water, scleractinian coral

What environmental factors set the boundaries for reef habitat locations?

Limited at high latitudes due to low temperatures, not enough sun, Low aragonite levels, and competition with temperature fauna

Limited at depths due to lack of light, temperature, and bioerosion

Benefits between the symbiosis of Scleractinian corals and their endosymbiotic microalgae?

photosynthate materials (carbs, lipids, amino acids) excreted by algae

protection and nitrogenous waste provided by host

In addition to corals what other taxa engage in similar symbiotic relationships with microalgae?

octocorals, sea anemones, jellyfish, sponges, molluscs, foraminifera, flatworms

Is the symbiont community the same for all organisms or within a single species?

Not the same for all organisms. Some may have multiple types and others may have one type

Not necessarily all the same across a species, but can be.

What factors drive the level of similarity between two symbiont communities are?

Varies by species

biogeographic patterns

some clades are associated with higher tolerances to stress

?????

There is a center of high biodiversity of shallow water marine organisms centered around Indonesia, Malaysia, the Philippines, and Papua New Guinea, and a gradient of reduced biodiversity away from this center. What is one of the main hypotheses for this gradient and the logic behind it?

The large amount of shallow-water habitat in this area

Supported by the

How do wave energy, SST, and levels of primary production shape how a reef community is likely to appear?

higher wave energy=low-laying coral and increased grazing

higher SST= support more coral and increased detrivores

Higher PP= more microbes, high coverage of calcifying benthic organisms, increased food consumption for fish and increased fish biomass

Explain the shift from coral-dominated to algal-dominated communities.

coral gives increased structure, more grazing, increased fish recruitment, reduced macroalgae, more coral = positive feedback loop

reduced coral, reduced structure, too little grazing, reduced fish recruitment, reduced grazing, increased macroalgae, decreased coral recruitment= negative feedback loop

What are the 2 leading hypotheses of the cause of crown-of-thorn (COT) outbreaks?

Primary outbreaks: Suddenly all pop up after a period of rarity. Due to change in environmental condition

Secondary: Hella larvae from the primary outbreak= a second generation

In terms of coral community structure, what have been the impacts of coral bleaching events on the Great Barrier Reef?

physiologically and nutritionally compromised coral

Corals that survive a bleaching event have thicker tissues and higher mass transfer

????

Fringing reef

borders shoreline directly

Barrier reef

border shoreline with a lagoon between shore and reef

Made of three zones: back reef, reef crest, fore reef (going outwards)

Atoll

reef forms around volcanic island and continues after volcano sinks below sealevel

island erosion, island sinking, reef accretion

Free living coral

single polyps

branching coral

usually fastest growing

plate-like coral

often found in deep water

Massive/lobed coral

usually slower growing and k-selected

Encrusting coral

tolerates higher physical disturbance but sometimes parasitic

Foliaceous coral

delicate; usually found in deep water

Potential causes for coral bleaching

thermal stress, too much sun, low salinity, hypoxia, too much sediment, prolonged subaerial exposure, bacterial infections, chemical pollutants

What were the main factors causing thiscoral-algae phase shift in the Caribbean, particularly Discovery Bay, Jamaica?

overfishing, hurricanes, eutrophication, disease

Overfishing of herbivorous fish, coastal eutrophication, hurricanes, sea urchin die-off due to bacteria, White-Band disease (coral)

Alternate stable states: Phase shifts

A positive feedback loop keeps the habitat solid, but after too many negative occurrences tipping point occurs and the negative feedback loop starts

Difficult to move between loops and hard to predict when the tipping point will occur that switches the loops

Kelp forest and urchin barren alternate stable states