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Oceanography Dr. Jackson

Terms

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Photostomias guernei
A deep⬐sea fish with a biological light.
Biozones – functional divisions
Euphotic zone extends from surface to where light can still support photosynthesis; to about 100 m ⬢ Disphotic zone extends to about 1000 m and have small but measurable amount of light ⬢ Aphotic zone extend to depths greater than 1000 m where there is no light
Marine Organism’s Environment
Density • Viscosity – Physical Support‐ drag • Salinity – Osmosis • Nutrient • Light • Temperature • Size
Plankton
Phytoplanktonplants Zooplanktonanimals Bacterioplanktonmicrobes
Salinity Effects
Organisms that have evolved a tolerance for a wide range of salinities are called euryhaline ⬢ Organisms adapted to little salinity change are called stenohaline
Osmosis
Passage of water through semipermeable membrane ⬢ Membrane separates to solutions of different solute concentration
Osmotic Regulation
When the salinity of an organisms fluid is equal to that of the surrounding ocean water, it is called isotonic ⬢ Hypertonic (saltier) and hypotonic (less salty) organisms experience osmotic pressure ⬢ Adaptations needed to regulate osmotic pressure
Solar Radiation
Solar radiation penetrates to greatest depth in the ocean compared with most coastal waters ⬢ However, most highly productive waters are in found in coastal areas, pointing to importance of nutrients
Temperature Adaptation
Organisms that can only withstand small temperature changes are called stenothermal and are found in open ocean and at depths ⬢ Organisms that can withstand large temperature changes are called eurythermal and are characteristic of more shallow waters
Species Distribution on Earth
Only 17 % of species live in the ocean ⬢ Most species live in the benthos ⬢ Uniform conditions of the open ocean do not force organisms to adapt, change ⬢ Although fewer species, ocean is more varied.
Benthic vs planktonic plants
Benthic plants are attached to the bottom. 􀂄 Mostly large plants (macrophytes) 􀂄 Marine plants do not stand up to the waves and currents but bend. Planktonic plants are freely floating plants 􀂄 Mostly single celled (phytoplankton or microphytes) 􀂄 Drift with the currents
Seagrasses
The roots and horizontal stems (rhizomes), often buried in sand or mud, anchor the grasses and absorb nutrients. 􀂄 Leaves, usually green, are produced on vertical branches and also absorb nutrients.
What is primary productivity?
􀂄Primary productivity is the rate at which energy is stored by organisms through the formation of organic matter (carbon compounds). 􀂄The energy comes from solar radiation (photosynthesis) or chemical reactions (chemosynthesis). 􀂄99.9 % of the ocean’s biomass get their carbon directly or indirectly from photosynthesis. 􀂄Except that produced by chemosynthetic organisms; such as those around hydrothermal vents and deep-sea archaea that oxidize hydrogen sulfide and methane to synthesize food.
Biological productivity
􀂄Primary producers are those organisms that photosynthesize their own food from water, carbon dioxide and the energy of solar radiation. 􀂄Photosynthetic primary producers include marine plants, macroalgae (seaweed), bacteria and microalgae (microscopic algae). 􀂄Most inorganic carbon is fixed by phytoplankton; microscopic algae and bacteria floating around in sunlit surface waters.
What do we measure?
Measure for a “short” time, so that do not worry about system changing during the measurement. 􀂄 If we want to know how much plant production is feeding the rest of the system, need to account for plant respiration.
How do we express it?
Want to standardize on a unit area (m2). 􀂉 Would like to be able to see how efficiently plants are using light, which we measure per unit area. 􀂉 Would like to make a “fair” comparison between Galveston Bay and Gulf of Mexico to see which is running faster, without worrying about the fact that the GoM is much bigger.
Types of photosynthetic productivity:
􀂄Gross primary production – rateof organic carbon produced by photosynthesis. Usually expressed either as a mass per unit area per time ( e.g., g C m-2 d-1) or chlorophyll per unit volume (mg m-3 d-1 or μg L-1 d-1). 􀂄Net primary production – what remains after the photosynthetic organism has satisfied its needs in terms of cell maintenance through respiration. 􀂄Net primary production is gross primary production minus cellular respiration and is manifested as growth, reproduction, release of dissolved organic compounds.
Measuring primary production: start by measuring plant biomass.
􀂄Plankton nets can be used to sample the plankton. Tells us what is present, not how fast they are growing. 􀂄Phytoplankton biomass can be estimated by using chlorophyll (green pigment used in photosynthesis) by capturing phytoplankton on filters and measuring the amount of chlorophyll captured. 􀂄Phytoplankton biomass is also measured using satellite instruments to measure ocean color, which is strongly affected by the presence of chlorophyll containing phytoplankton.
Measuring productivity
Rates of productivity can be estimated by measuring photosynthesis rates and respiration rates. 􀂄Photosynthesis rates usually measured by the production of oxygen or the assimilation of inorganic carbon into organic carbon. 􀂄Oxygen production (photosynthesis) and uptake (respiration) can be measured by enclosing samples of seawater in bottles and measuring the change in oxygen concentration in the bottles.
Oxygen Method
Gross primary production is the total amount of organic matter produced per unit of time 􀂄 Net primary production is what is left after respiration 􀂄 Change in oxygen 􀂉 Light bottle: photo-resp 􀂉 Dark bottle: -resp
Divide gross primary production into two components:
􀂄New production – generated using nutrients brought in from outside the local ecosystem by processes such as upwelling. 􀂄Regenerated production – generated using nutrients that are recycled within the system. 􀂄As the ratio of new production to gross primary production increases, so does the ecosystems ability to support animal populations. 􀂄Explains why upwelling areas, such as the in the coastal water off Peru (chapter 7) are such valuable fishing grounds. 􀂄New production – generated using nutrients brought in from outside the local ecosystem by processes such as upwelling. 􀂄Regenerated production – generated using nutrients that are recycled within the system. 􀂄As the ratio of new production to gross primary production increases, so does the ecosystems ability to support animal populations. 􀂄Explains why upwelling areas, such as the in the coastal water off Peru (chapter 7) are such valuable fishing grounds.
Light transmission in ocean waters
􀂄Ocean selectively absorbs visible light of the longer wavelengths (red, orange and yellow). 􀂄Red light usually absorbed within the upper 10 m of ocean. 􀂄Yellow absorbed by about 100 m. 􀂄Shorter wavelengths (e.g. blue) penetrates the ocean to a greater depth.
Photosynthetic organisms – microscopic algae
Most microscopic algae are phytoplankton. 􀂄Produce food directly or indirectly for 99 % of marine animals. 􀂄Diatoms – important primary producers, cells contained within a test of silica. 􀂄Coccolithophores – covered in small calcareous plates called coccoliths. 􀂄Dinoflagellates – use flagella for locomotion, therefore have a slight capacity to move themselves into more favorable light and nutrient conditions. Sometimes exist in great abundance and color the water, producing a red tide, which is more accurately termed a harmful algal bloom (HAB). 􀂄Dinoflagellates are associated with various types of food poisoning, including ciguatera, caused by eating tropical reef fish which contain high levels of naturally occurring dinoflagellate toxins.
Biotic Community
Assemblage of organisms that live together within some definable area 􀀩 Ecosystem = biotic community + environment
Ecosystem
Producers - algae and some bacteria 􀀩 Consumers - heterotrophs 􀀩Decomposers - heterotrophs (mainly bacteria, some fungi)
Consumers
􀀩 Herbivores 􀀩 Carnivores 􀀩 Omnivores 􀀩 Bacteriovores
Symbiosis
􀀩 Two or more organisms closely associated such that at least one or more benefits from this association 􀀩 Corals – Animal feeding on particles – Algae photosynthesizing 􀀩 Green sea anemones at shore line
Types of Symbiosis
􀀩Commensalism - smaller or less dominant participant benefits without harming its host 􀀩 Mutualism - both participants benefit 􀀩 Parasitism - the parasite benefits at the expense of its host 􀀩 Mutualism extremely common among marine organisms (tending a garden)
Energy Through Trophic Levels
Energy flow is unidirectional 􀀩 Ultimately, energy goes to heat 􀀩 As biomass moves through the food chain, there are losses such that a small percentage ultimately reaches the highest trophic levels
Biogeochemical Cycle
􀀩 Inorganic nutrient is used to make organic matter by autotroph – Photo-autotroph- use light energy to make organic matter – Chemo-autotroph- use chemical energy to make organic matter (eg, bacteria that use sulfide as energy source, use) 􀀩 Heterotrophs require organic matter to grow
Trophic transfer in the sea
Animals tend to feed on food 10% of their size 􀀩 For food to get to a size we can eat, it might go through 4-5 steps. 􀀩 If four steps, we get 0.1 x 0.1 x 0.1 x 0.1= 10-4=0.0001 of original food 􀀩 The closer we eat to the original plant, the more energy efficient.
Marine Productivity
Plant growth fuels the growth of all animals 􀀩 Plant growth in the ocean usually limited by either insufficient light or low nutrient concentrations (N, P) 􀀩 Nutrients are stripped out of the surface water by plant growth, settling to deeper water 􀀩 Result is low surface nutrient concentration at surface
Marine productivity-2
Growth requires the movement of nutrients to the surface 􀂋Gentle, slow mixing 􀂋Upwelling 􀂋Winter mixing 􀀩 Runoff from the land can also add nutrients, support plant growth
Gulf of Mexico- interlude
Highest productivity next to coast 􀀩Mississippi River is a big provider of nutrients, affects Texas shelf to Mexico 􀀩 Center of Gulf can be quite sterile 􀀩 Highest biomass in winter, when weather increases mixing 􀀩 Can see effect of Loop Current on central Gulf
Fundamental constraints
Animals feed by capturing other particles (phytoplankton, animals, detritus) ⬢ Size of feeder/size of food ~ 10 ⬢ Big things are rarer. Need to be able to search larger volumes of water. ⬢ Will be true for benthic as well as planktonic animals.
Benthic Animals
• 98 % of ocean animals live on the ocean floor • The majority of benthic species are found on the continental shelf • Must adapt to: – conditions in overlying seawater – conditions in sediments – pressure from other organisms
Needs for life in the benthos: food
Photosynthesis‐ confined to shallow regions next to coast (seaweeds) • Particles falling from overlying water – Directly‐ grab from water (suspension feeding) – Indirectly‐ eat what falls to bottom – Problem: most eaten on the way to the bottom • Eat someone else • Oxidize chemicals (microbes/chemoautotrophs)
Needs for life in the benthos: home
Need to be able to hold on when water flows. – Attach to surface, particularly in intertidal • Needs to be hard rock, else float away – Burrow into sand • All the time‐ can be harsh chemically (no oxygen) • When conditions get bad • As anchor (e.g., sea pen) • Live in a tranquil environment (deep sea)
High Intertidal
The upper intertidal zone has the widest range of heat and cold. desiccation in the summer, freezing in the winter. ⬢ Fresh water, both surface water from rainfall and subsurface flow, can impact populations. ⬢ With limited inundation time, marine food resources are limited. ⬢ Mostly scavengers, which rely on "islands" of wrack material for sustenance.
Mid Zone
The mid⬐littoral zone is characterized by a moderate inundation time, but is subject to many of the same rigors as the upper zone (temperature extremes, fresh water). ⬢ The mid zone is more subject to rapid sediment removal during winter storms, requiring extreme mobility of its fauna.
Mid⬐Intertidal
The mid⬐intertidal zone is exposed to air briefly once or twice a day ⬢ At wave⬐exposed sites, the mussel, Mytilus, can dominate the available attachment substratum. ⬢ Also starfish.
Low Intertidal Zone
The low intertidal zone, extending into the shallow subtidal, is almost fully marine, being aerially exposed for short periods only on the lowest tides. ⬢ The low intertidal is subject to almost constant wave action, requiring that the inhabitants be either rapid burrowers (e.g. Blepharipoda) or protected against mechanical damage (e.g. Tivella). ⬢ It houses the most diverse faunal assemblage of the beach zones.

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