Biological Oceanography

Front 1

What are growth trends among and within fish species?

Back 1

Growth is variable among and within species, and even within a population.

Von Bertalanffy growth model follows a differential function.

Front 2

What are the common themes found in fish reproduction?

Back 2

- Separate sexes, release of small eggs (1-2 mm)
- Spawning occurs at specific times and places
- Reproduction is synchronized with environmental parameters, especially temperature and circulation patterns
- larvae, juveniles, and adults occupy different habitats
- extensive migration can occur

Front 3

How are fish "stocks" defined from a metapopulation perspective?

Back 3

The metapopulation of stocks are a set or constellation of local populations that are linked by dispersal
- Fish are usually studied (and managed) as stocks, separate, genetically distinct, local populations
- There tend to be ecological, phenotypic, and genetic differences between stocks
- Stock definition -- "a group of freely interbreeding fishes occupying a particular space and time"

Front 4

How are distinct fish stocks identified?

Back 4

- Tagging studies -- spawning site fidelity, mixing.
- Artificial tags
- Natural tags (e.g. otolith chemistry, parasites)
- Phenotypic characters
- Molecular genetics

Front 5

What are otoliths?

Back 5

Otoliths are structures in the inner ear that are sensitive to gravity and linear acceleration. They are used as gravity, balance, mood and direction indicators.

Otoliths are created from calcium carbonate. Measuring the aragonite or (sometimes) vaterite crystals formed allows scientists to measure trace elements and isotopes that have bound to those minerals, and to thus determine what bodies of water the fish has lived in/moved through.

Front 6

What are general characteristics of fish populations?

Back 6

- Natural fluctuations
- Age class dominance (some cohorts may benefit from more advantageous environmental conditions, variations in cohort production/fecundity of parents)
- Recruitment -- variation in year class success

Front 7

What is the Maximum Sustainable Yield in terms of fisheries?

Back 7

The maximum catch that can be taken without the population crashing; "[t]he "Holy Grail in fisheries science was to find the maximum sustainable yield" - Jennings et al. 2001

Front 8

How is fish recruitment calculated?

Back 8

Beverton-Holt: R=aS/1+bS

Recruitment increases to asymptote with increasing spawner abundance

Ricker: R=aSe to the -bs power
* Includes density dependent mortality at high spawner abundance

BUT -- huge amount of variation in recruitment. Spawner-Recruit relationships are notorious for being messy, with several potential reasons for variability.

Front 9

How are fish populations regulated?

Back 9

- Density-dependent factors (predictable):
competition for resources (food supply, territory) leading to changes in growth, fecundity and mortality

- Density-independent factors (unpredictable and stochastic):
- Oceanic circulation (larval transport), other physical processes
- Regime shifts or other coupled ocean-atmospheric processes (ENSO)

Front 10

What is the Benguela upwelling zone?

Back 10

The marine area immediately off the southwest coast of Africa. A southeast wind moves up the coast, and surface water is pushed away from shore by Ekman transport. Nutrient-rich water then upwells.

Front 11

What is Ekman drift?

Back 11

Net movement of wind-driven flow is 90 degrees to wind; this movement is to the right in the Northern Hemisphere, to the left in the Southern, due to the Coriolis Effect. Transports water offshore when the wind blows parallel to the coast and toward the equator.

Front 12

What are the primary upwelling regions discussed in class?

Back 12

Northern Hemisphere: California (Pacific) and Canary (Atlantic).
Southern Hemisphere: Peru/Humboldt (Pacific) and Benguela (Atlantic).

Front 13

What are the consequences of offshore Ekman transport?

Back 13

Surface water removed by offshore drift must be replaced. It can't come horizontally because of coastal boundary, so it must come from below and offshore. This water may be cooler and higher in nutrients, depending on how deep the thermocline is. This may fuel increased primary productivity if light/mixing are also favorable.

Front 14

What does a schematic of upwelling processes look like?

Back 14

Front 15

What influences the rate of upwelling?

Back 15

1. Changes in strength and direction of driving winds;
2. Vertical structure of the water column (mixed layer depth, source of deeper water);
3. Ocean bottom topography (canyons, shelf slope); and
4. Large-scale current structure.

"Rate" may refer to water movement or nutrient supply, depending on the discussion at hand.

Front 16

What does the zonation in the Peruvian upwelling system look like?

Back 16

1. Intense upwelling, high nutrients, but low uptake (phytoplankton not 'ready')
2. Water column stabilizes, rapid nutrient uptake (phytoplankton 'shift-up')
3. Biomass accumulation, maximum primary productivity
4. Nutrient depletion (phytoplankton 'shift-down')
Time scale: 8-10 days from Zone 1 to 4.

Front 17

How is the Canary upwelling system different than the Peruvian upwelling system?

Back 17

* Canary has broader, shallower shelf (50 vs. 20 km)
* Canary has lower source water nutrients (5 micromolar of nitrate vs. 20 micromolar of nitrate)
* Canary has stronger but less predictable winds; deeper mixed layer only allows blooms to develop between wind events (when surface mixed layer becomes shallower than critical depth)

Front 18

How does copepod life history relate to upwelling regions?

Back 18

* Copepods use physical upwelling and swimming (or sinking)
* Life stages coincide with bloom development (eggs nearshore, nauplii go closer then go out, maturity out at ~25 km)

Front 19

What other upwelling systems are there besides the California, Peruvian, Canary, and Benguela?

Back 19

Also more temporally and spatially more restricted coastal upwelling in Indian Ocean (monsoon-driven). Non-coastal upwelling occurs in Antarctic, Equatorial Pacific, and eddies).

Front 20

How does Antarctic upwelling occur?

Back 20

Through divergence; "east wind drift" around Antarctica plus the Coriolis drives coastal downwelling. "West wind drift" (Antarctic Circumpolar Current) plus Coriolis pushes surface waters the other way. Upwelled water in Antarctic can extend from coast to the polar front (50 degrees south latitude)

Front 21

How does the equatorial upwelling work?

Back 21

Front 22

How does El Niño affect nitrate concentration in the equatorial upwelling system?

Back 22

Results in significant decrease in chlorophyll at equator surface waters during El Niño events.

Front 23

What are the take-away points from the Irarte and Gonzalez 2004 paper on El Niño and primary production?

Back 23

Research was undertaken in northern Chile. During "normal" (La Niña) upwelling, primary production and bulk chl are relatively high and variable, and dominated by large, chain-forming diatoms. During 1997/1998 El Niño, primary production and bulk chl were relatively low, and dominated by smaller (less than 20 micron phytoplankton).

Front 24

What are the take-away points from the Irarte and Gonzalez 2004 paper on El Niño and primary production?

Back 24

Research was undertaken in northern Chile. During "normal" (La Niña) upwelling, primary production and bulk chl are relatively high and variable, and dominated by large, chain-forming diatoms. During 1997/1998 El Niño, primary production and bulk chl were relatively low, and dominated by smaller (less than 20 micron phytoplankton).

Vertical flux rate of autotrophs decreased significantly during El Niño.

Front 25

What are the take-away points from the Chavez et al. 2003 paper on regime shifts?

Back 25

Landings of sardines show synchronous variations at multiple locations; populations flourish for 20 to 30 years then practically disappear for similar periods, with that disappearance marked by dramatic increases in anchovy populations. This is due largely to climatic shifts.

Front 26

What is ecosystem oceanography and how is it distinguished from fisheries oceanography by Cury et al.?

Back 26

Ecosystem oceanography represents a balanced strategy that relates ecosystem components and their interactions to climate change and exploitation to develop realistic and robust models. Unlike fisheries oceanography it does not only divide controls of fish stocks into bottom-up and top-down forces.

Front 27

What percentage of the world fish catch comes from upwelling regions?

Back 27

~50%

Front 28

What are clupeiformes?

Back 28

Small schooling fishes (e.g. anchovies, sardines, herring, menhaden). Primarily planktivores, with major economic value and characterized by boom/bust fisheries.

Front 29

What population changes were seen in Peruvian upwelling region species during El Niño?

Back 29

(from Taylor et al. 2008, fig. 3)

Hint 29

Diatoms saw a decrease in favor of dino- and silicoflagellates. Sardine and anchovies both saw an overall decline, while jumbo squid showed an increase, and seabirds and pinnipeds saw a slight downward slope though this trend outlasted El Niño.

Front 30

How are ecosystems described?

Back 30

Ecosystems can be described by trophic interactions of organisms:
-- Pathways of energy
-- Pathways of material

Front 31

What is a trophic cascade?

Back 31

"...propagation of indirect mutualism between nonadjacent levels in food chain..."

Front 32

What is a trophic reversal?

Back 32

Predators of juveniles become the prey of those surviving to adulthood.

Front 33

What are top-down and bottom-up controls?

Back 33

Top-down: predation
bottom-up: nutrient and/or energy controls

Front 34

What constitutes a trophic level?

Back 34

Organisms that obtain their material and energy in a similar manner.

Front 35

What does the Peruvian upwelling food web look like?

Back 35

"Wasp-waisted" with anchoveta at the "waist."

Front 36

What does the energy transfer between trophic levels look like?

Back 36

Front 37

How is exploitation efficiency defined?

Back 37

Ingestion of food / prey production

Exploitation efficiency is the efficiency with which an entire trophic level is consumed; how much production moves to the next trophic level. A high exploitation efficiency might be seen where most phytoplankton are eventually eaten by a herbivore, with low exploitation efficiency seen where there is significant export to bottom for sequestration.

Front 38

How is assimilation efficiency defined?

Back 38

Assimilation / ingestion

Assimilation efficiency is the portion of consumed energy which is actually assimilated. For example, terrestrial herbivores eating plants tend to have lower assimilation; not all of the plant can be used.

Front 39

How is net production efficiency defined?

Back 39

Production (growth and reproduction) / assimilation

This measures how efficiently assimilated energy is incorporated into growth, storage and reproduction.

Front 40

What is ecological efficiency?

Back 40

The conversion of prey into predator biomass.

Calculated by:
(exploitation efficiency) * (assimilation efficiency) * (net production efficiency)

Equivalent to consumer production / prey production.

Front 41

What are the approximate growth efficiencies of different trophic structures?

Back 41

* Bacteria have ~50% growth efficiency (with reported range of 5% to 90%)
* Heterotrophic protozoans have ~40% efficiency (reported range 20% to 82%)
* Copepods have ~20% growth efficiency (reported range 10% to 40%)

Higher trophic levels have lower growth efficiencies due to larger body size.

Front 42

What is food chain efficiency?

Back 42

Generally ~10%. 10,000 unites of phytoplankton > 1,000 units of zooplankton > 100 units of planktivore > 10 units of carnivore > 1 unit of human mass.

Front 43

What determines the number of trophic levels from primary producers to top predators?

Back 43

* Size of primary producers
* Species diversity

Front 44

How do upwelling food webs differ from gyre food webs?

Back 44

Upwelling regions have higher Trophic Level 1 production due to upwelled nutrients, and this production is dominated by larger diatoms. Large phytoplankton are eaten by larger zooplankton or small fish directly.

This results in:

Shorter food chain AND more efficient food chain.

Upwelling areas also support the most important commercial and industrial fisheries (also important food webs supporting large nekton, birds, and mammals).

Front 45

What are some common traits of polar systems?

Back 45

-- High seasonality in light.
-- Very low water temperatures (-1.8 degrees C)
-- Sea ice, important for physics, optics and biology.

Front 46

What is sea ice?

Back 46

Seawater begins to freeze at -1.8 degrees celsius. Ice cover varies seasonally.

Ice crystals exclude salt, so brine concentrates in channels and is eventually transferred to seawater, increasing seawater salinity, and brine channels are filled with liquid brine.

Front 47

What is in sea ice?

Back 47

Life in sea ice is in an extreme environment. Liquid brine channels are colonized by organisms, including algae. The underside of ice is a habitat for algae and animals.

Front 48

What is sea ice's effect on production?

Back 48

Stratification due to ice melt allows intense phytoplankton blooms. As ice continues to recede, bloom diminishes and is subducted, resulting in subsurface chl maximum.

Front 49

What are the characteristic of the Arctic ocean and its seas?

Back 49

Broad, shallow seas with high seasonal production surrounding a deep basin. Seasonal sea ice production occurs on shelves, there is lots of riverine input of fresh water, nutrients, and organic matter.

In addition to the broad shelves, there are several deep basins which are (currently) ice covered year round.

Front 50

What role do gray whales have in polar areas?

Back 50

Largest benthic predator; they bite the sediment and sift out benthos. They are also important in releasing nutrients into the water column.

Front 51

What are the characteristics of the Southern Ocean (Antarctic)?

Back 51

Ocean currents surrounding an ice-covered continent, with little terrestrial input of fresh water and nutrients and relatively narrow shelves.

Front 52

What limits production in polar regions?

Back 52

Likely factors include termperature and light. Even though it is permanently cold, however, temperature does not limit Trophic Level 1 or Trophic Level 2 production. Seasonality of production limits total production to short periods; some regions are ice free for one month (or less), and growth and metabolic rates can be high (for example, benthic communities rapidly use algae).

Front 53

What are the characteristics of the polar microbial loop?

Back 53

Bacteria may be less important in polar oceans than elsewhere, with lower biomass and production. This may be due to organic matter availability, temperature, or mortality.
Bacterial production is relatively insensitive to temperatures above 4 degrees celsius, but below 4 degrees production can increase rapidly with heating, though this is quite variable. However, bioavailable DOC appears to differ in polar oceans, suggesting that substrate controls bacteria production in polar oceans more than temperature.

Grazing and detrital food webs may be more important.

Front 54

How does low temperature limit grazing?

Back 54

Protozoa and copepods are affected more by low temperatures than phytoplankton. This may contribute to polar blooms.

Front 55

What characterizes polar food webs?

Back 55

Polar food webs are lipid food webs. Energy flows are dominated by lipid content. Lipid storage is critical to overwintering.

Front 56

What is the relationship between calanus glacialis food sources and lifecycle?

Back 56

Calanus glacialis uses ice algae to fuel reproduction, and phytoplankton bloom to support larval and juvenile growth.

Front 57

What are characteristics of copepod life history in the polar regions?

Back 57

Seasonal migration (vertical) and diapause; arctic species must diapause several times before attaining maturity.

Front 58

What are characteristics of krill?

Back 58

Dominate antarctic food webs: strong swimmers, schooling, long-lived, commercially harvested. Different life stages move vertically and laterally and sea ice plays a role in krill development as food source and refuge. Krill are long-lived with occasional good year class recruitment, associated with extensive sea ice (as opposed to short-lived salps, more abundant after reduced sea ice).

Front 59

What are the take-away points from Smetacek and Nicol 2005?

Back 59

Polar organisms have adapted their seasonal cycles to the dynamic interface between ice and water. This interface ranges from the micrometre-sized brine channels within sea ice to the planetary-scale advance and retreat of sea ice.

Front 60

What are the take-away points from the Wassman and Reigstad 2011 article on the effect of climate warming on the arctic?

Back 60

Climate warming will likely cause the largest changes in the northern portions of today's seasonal ice zone, which will expand to cover the entire Arctic Ocean, and the southern portions, which will be exposed to more thermal stratification. While the former will increase productivity and supply to the bottom, the latter will decrease those things. Blooms will weaken in the seasonal ice zone, resulting in lower average food concentrations for pelagic heterotrophs, with more available energy recycled in the pelagic zone and corresponding less variable and reduced quality vertical export of biogenic matter. Increased freshwater discharge from rivers will introduce more nutrients, but turbidity will increase from melting permafrost, possibly lowering primary production. Community composition will move towards smaller forms, more recycling, and reduced pelagic-benthic coupling.

Front 61

What are the characteristics of climate change in polar oceans?

Back 61

Some polar regions, especially the NW Pacific and Western Antarctic Peninsula are warming faster than the global average. These regions are also responding to historic declines in whale populations and to decadal climate shifts. In the Southern Ocean, krill declines correlate with change in ice cover.

Front 62

Why would iron be limiting?

Back 62

All living things use iron to move electrons around in various redox reactions. Why iron is the 4th most abundant element in the crust (behind oxygen, silicon, and aluminum) and accounts for >5% of the weight of Earth's crust, it is not very soluble in our modern, oxygenated (oxidizing) slightly basic pH oceans. Soluble Fe may be low enough to be limiting in 25% of the ocean's surface.

Why some phytoplankton can increase their ability to scavenge iron from the environment by producing and releasing compounds (siderophores) that make iron more available, and some phytoplankton can change over to enzymes that do not require Fe, some Fe is essential. Species present in an Fe-limited system will reflect a response to Fe limitation.

Front 63

What are the sources of Fe to the ocean?

Back 63

* Rivers (coastal only and quickly lost to sediments)
* Resuspension of particles from sediments (coastal)
* Upwelling of deep water
* Atmospheric deposition (as dust, though overall levels are low and less than 10% of it is soluble; levels were 10X higher during last glacial max).

Front 64

What did the iron fertilization experiments show concerning HNLC waters?

Back 64

Iron is limiting, but that is not the whole story. Phytoplankton biomass increased drastically in 1993 IronEx I experiment, but the increase did not last long partly because Fe became bound in particles and sank, and partly because zookplankton quickly "caught up." A second element (Zn or Si?) may also have become limiting, and there was not much change in carbon dioxide, with onl 10% of the amount expected "removed."

IronEx II supports the "ecumenical" iron hypothesis, which states that Fe and grazing co-regulate phytoplankton in HNLC regions. Dominant picophytoplankton were Fe-limited in the sense that their physiology changed with Fe addition, but their abundance was grazing limited. However, total production was iron-limited in the sense that adding more iron allowed larger phytoplankton to grow, fundamentally changing the ecosystem.

Front 65

How did IronEx II measure phytoplankton response to iron fertilization? What did it find?

Back 65

* By bulk extracted Chl a (index of biomass) (though this may not be a good measure of biomass if Chl per cell changes)
* By in vivo fluorescence (Fv/Fm)
* By size (filtration and microscopy)
* By other types of pigments (HPLC analysis)
* By flow cytometry (size and pigment)
* By taxonomy (flow cytometry and microscopy)

Concentrations of chlorophyll increased by ~10-fold, causing the water in the patch to turn visibly green.

Front 66

What is the phytoplankton species composition of HNLC areas? What happened to species composition after adding Fe?

Back 66

Usually dominated by picophytoplankton with cells < 2 microns, and other small phytoplankton, including cyanobacteria (prochlorococcus, synechococcus), and small eukaryotes (<5 or 10 microns).

Together these smaller organisms contribute >90% of total Chl a.

After adding Fe small phytoplankton get healthier (increased pigment per cell and cell volume, more siderophores producted) but not much more abundant due to high grazing pressure and rapid response of grazers However, cells greater than 10 microns increased dramatically, coming to contribute >60% of total Chl a (or more, since skinny diatoms can go through 10 micron filter pores). Diatoms constituted a large part (if not all) of increase. Decline in this bloom may be caused by a variety of factors (grazing, sinking, Si or light limitation).

Front 67

What are the take-away points from the Lavery et al. 2010 article on sperm whale iron defecation?

Back 67

That the argument that marine mammal respiration decreases the efficiency of the Southern Ocean biological pump by returning photosynthetically fixed carbon to the atmosphere is incorrect. Sperm whales stimulate carbon export through iron defecation, acting as an overall carbon sink.

Front 68

What issues must be addressed when analyzing coastal food webs? How are food web analyses carried out?

Back 68

Coastal food web analysis is complicated by several primary food sources that differ in delivery, quality, and temporal persistence.

Food web analyses can be done through gut contents, stable isotope analysis, and biomarkers (especially fatty acids).

Front 69

What are sources of coastal organic matter?

Back 69

Phytoplankton, benthic microalgae and macroalgae, seagrasses and salt marsh grasses, and land-derived organic matter.

Sources differ in availability, digestibility, nutritional quality, and temporal availability, with some foods available primarily as detritus, and with many animals moving between habitats, using different sources at different times.

Front 70

How is gut content analysis done?

Back 70

Traditional method of determining diet, especially of fish and other larger animals. Involves microscopic identification of remains (scales, shells, etc.). It is valuable for examining feeding selectivity, but for many animals the largest fraction in the guy is unrecognizable mush. Other means of identification include immunoassays, DNA, biomarkers, etc.

Front 71

What are detritus-based food webs?

Back 71

Many coastal food webs are (at least partially) fueled by detritus. Detritus sources include phytoplankton, seaweeds, marsh and sea grasses, mangroves, soil organic matter, and sewage. A few sources of detritus may support many species of "grazers." With algal-based detritus there is a race between grazers and decomposers, but with plant-based detritus few species use live (or even dead) substrate directly, instead relying on microbial transformations.

Front 72

What are the characteristics of phytoplankton detritus?

Back 72

Decays very quickly, within days, rapidly losing its nutritional value. Poor quality detritus (from cyanobacteria) can improve in nutritional quality by the growth of microeukaryotes (bacterial grazers), a process called trophic upgrading, though those microeukaryotes do reduce the amount of organic matter available to the next trophic level.

Front 73

What are the characteristics of seaweed detritus?

Back 73

Many seaweeds are too big, too tough, and too chemically defended for many marine animals to use directly. Seaweed detritus decomposes over weeks, and may improve in nutritional quality as polyphenols leach out (quality increases as phenolic content declines). Processes that break up seaweeds are important in detritus production and fate. In fact, amphipods survived and grew better on Laminaria that had been microbially degraded.

Front 74

What are the characteristics of salt marsh grass detritus?

Back 74

Salt marshes are very productive of plants and animals, but most of the animals do not eat the plants. However, many marsh animals utilize spartina detritus and its attendant microbes (especially fungi). These specialist detritivores connect Spartina production to higher trophic levels. An example can be seen in fungal farming by a salt marsh snail.

Front 75

Where do seagrasses fall within the coastal food web?

Back 75

Subtidal seagrasses are habitats for algae growing on leaves. Many animals graze the algae, which improves seagrass access to light, though not many species graze directly on seagrass.

Front 76

What are the characteristics of mangrove detritus?

Back 76

Mangrove trees provide dead leaves to the detritus food web. The role of phytoplankton and mangrove detritus for barnacles in a Florida estuary based on multiple stable isotopes showed mangrove detritus accounted for ~60% of barnacle nutrition in mid-estuary, even though barnacles probably do not digest it directly. Some crabs eat dead mangrove leaves directly, and have cellulase and other special enzymes to process the leaves. Coprophagy is probably important in all detritus-based food webs.

Front 77

Where does terrestrial organic matter in coastal areas come from?

Back 77

Much of the POC in coastal muds is land-based and old, including soil OM, leaf litter, and DOM. Generally there is very low availability, but there are many exceptions:
1. Arctic peat or glacier-delivered POM becomes accessible when delivered to coastal ocean.
2. Freshwater animals may be important (lagoons).
3. Subsurface deposit feeders (role of microbes?)
4. Even OM in 365 MYA shale can be used when made accessible.

Front 78

What is benthic-pelagic coupling?

Back 78

B-P coupling usually refers to organic matter sinking to seabed, decomposing, and delivery of inorganic nutrients to the water column from the seabed by diffusion and mixing. B-P coupling can include:
-- the subtidal pump
-- planktonic larvae of benthos
-- benthic resting stages of plankton
-- benthic suspension-feeding

Front 79

What effect does temperature have on phytoplankton blooms?

Back 79

Under warmer conditions, zooplankton more easily keep up with primary production, and bloom is diminished. Therefore, warming winters show reduced benthic-pelagic coupling as material is recycled before it can be exported to the bottom.

Front 80

Where does energy (electrons) come from and where do electrons go when discussing heterotrophs?

Back 80

For aerobic respirers, O2 is the terminal electron acceptor. However, in anoxic environments, other electron acceptors are used (e.g. nitrate, sulfate, Mn oxides, Fe oxides, etc.)

Front 81

What is the process by which organic matter degrades?

Back 81

Front 82

What does the integration of biogeochemical and biological phenomena in benthic-pelagic coupling look like?

Back 82

Front 83

How do suspension feeders obtain food?

Back 83

Food diluted by water, with SF needing to process ("clear") lots of water, 10,000 to 100,000 times body volume a day. Food is a complex mixture, and suspension feeding has been invented many times in many taxa. Flow increases particle flux, which is good for suspension feeders.

Many SF actively pump water through particle-collection device (gill, mucus web, setae, etc.). Bivalves are among the most successful suspension feeders, constituting many commercially imported species. They use large, ciliated gills to make current, capture and sort particles. While SF used to be thought of as herbivores, SF now are known to eat microzookplankton, detritus, small macrozooplankton and eggs, bacteria, and particle-associated viruses.

Some species can switch between DF (especially at surface) and suspension feeding. Depends on flow/particle flux.

Front 84

What is stable isotope analysis and what is it used for?

Back 84

Stable isotopes are expressed in terms of delta values, which are parts per thousand differences from a standard. The two major isotopes used are 13C and 15N.

13C - helps determine the primary production source responsible for the energy flow in an ecosystem. Different food sources have different 13C delta values. As 13C moves up the food chain, increases in proportion by .5-1% per trophic level movement.

15N can show different trophic levels. As organisms eat each other 15N isotopes are transferred to the predators. Organisms higher in the trophic pyramid have accumulated higher levels of 15N relative to their prey. Delta 15N values also help distinguish between land derived and natural sources of nutrients. 15N increases by 1-3% per trophic level transfer.

Front 85

What are the characteristics of phytoplankton blooms in Long Island Sound?

Back 85

Diatom blooms in February/March; controlled by light, with nutrients that accumulated over the winter

Front 86

What are the types of benthic coupling?

Back 86

Demersal Zooplankton:
"mobile, benthic organisms which periodically emerge from the benthos and move up into the water column" including ostracodes, copepods, and amphipods.

Subtidal Pump: Interstitial water exchange by wave action

Nutrient remineralization: bacteria in bottom sediment are important in remineralization (the transformation of organic molecules to inorganic forms) through aerobic respiration using dissolved oxygen as electron acceptor and anaerobic processes using a variety of inorganic species (i.e. nitrate, nitrite, manganese and iron oxides, sulfate).

Benthic Suspension Feeding: Bivalves and polycheates are examples of suspension feeders that feed by straining particles from water usually over specialized structures where they are digested and expelled as feces or pseudofeces

Front 87

What is the subtidal pump?

Back 87

Interstitial water exchange by wave action. In water sufficiently shallow for wave action to penetrate to the bed, pressure tends to be relatively high under the wave crests and relatively low under the troughs. These oscillatory pressure perturbations penetrate into the sediments, where the resulting pressure gradients induce interstitial motions.

The resulting pore water circulation brings organic matter and oxygen to the interior of the sediment, creates horizontal concentration gradients that can be as strong as the vertical gradients, and increases the flux of pore water constituents across the sediment-water interface.