biol and physical interactions

Describe planktotrophic larvae and lecithotrophic larvae? What are the main differences between them with respect to larval dispersal

Planktotrophic larvae feed on plankton in the water column during development. They typically come from many small eggs and have a longer pelagic larval duration, often lasting weeks. This allows them to remain in the water column longer and potentially disperse greater through ocean currents. Lecithotrophic larvae rely on stored yolk reserves for energy rather than feeding on plankton. They typically come from fewer, larger eggs and have a shorter pelagic larval duration, often lasting hours to days. Because they spend less time in the water column they generally disperse shorter distances.

What other physical / geochemical factors help determine pelagic larval duration-

pelagic larval duration is influenced by environmental conditions such as water temperature and food availability. Warmer temperatures generally increase larval development rates, shortening the time larvae spend in the water column. For feeding larvae, greater food availability can support faster growth and development, potentially reducing PLD. Colder Temperatures or limited food can slow development and increase the time larvae remain planktonic

Describe the benefits and disadvantages of coastal upwelling to dispersing barnacle larvae-

Coastal upwelling can benefit dispersing barnacle larvae by bringing nutrient rich deep water to the surface, increasing phytoplankton productivity and providing more food for larval growth and development. However, upwelling also causes offshore Ekman transport of surface water, which can carry barnacles’ larvae away from suitable coastal settlement habitats and reducing recruitment.

Why does the Oregon region of the West Coast USA have more barnacle recruitment than the California region?

Oregon has higher barnacle recruitment because coastal upwelling is weaker and more intermittent, allowing larvae to remain closer to shore while still benefitting from increased primary production. In central California, upwelling is stronger and more continuous, transporting surface water and barnacle larvae offshore through Ekman transport. This reduces successful recruitment because fewer larvae reach suitable coastal habitats. During relaxation events in California recruitment increases.

Why is phytoplankton patchiness and local concentrations such as in thin layers so important to the ocean ecology?

Phytoplankton patchiness and thin layers are ecologically important because they concentrate food resources in specific areas, increasing feeding opportunities for zooplankton. These concentrations attract organisms at higher trophic levels, including small fish and larger predators, allowing energy to transfer more efficiently through the marine food web. If phytoplankton were evenly dispersed predators would have greater difficulty locating sufficient prey, reducing feeding efficiency.

How is the stability of a front with convergence of phytoplankton related to the trophic levels found there?

The stability of a front influences the number of trophic levels that can benefit from the concentrated phytoplankton, short lived fronts may concentrate phytoplankton and attract zooplankton but may not persist long enough for larger predators to aggregate. More stable fronts maintain concentrated food resources for longer periods, allowing for zooplankton, fish, and larger predators to gather,

Describe and/or diagram the fronts that we discussed in class-

Upwelling – wind driven Ekman transport brings cold nutrient rich waters to the surface. Shelf break- forms near continental shelf break where different water masses meet, creating strong density gradients. Tidal mixing- tidal currents mix the water column, creating a boundary between well mixed and stratified waters. Topographic front- Forms when currents encounter features such as headlands, islands, or underwater canyons causing mixing and changes in flow. Plume front- forms when plume of water often freshwater from a river meets surrounding seawater. Estuarine- water masses with different salinities and densities meet within an estuary.

How do tidal mixing fronts create regions of higher productivity?

Tidal mixing fronts increase primary production by mixing stratified waters, bringing nutrient rich deeper water towards the surface. These nutrients become available to phytoplankton for photosynthesis.

What is the source of most of the radiance detected by a satellite sensor?

Most of the radiance detected by an ocean color satellite sensor comes from sunlight scattered by the atmosphere, accounting for more than 90% of the detected signal. Scientists must correct for atmospheric contributions to isolate the light coming from the ocean.

What factors influence the color of the radiance that comes from the interior of the ocean?

The color of radiance coming from the ocean interior depends on how different wavelengths of light are absorbed and scattered by seawater and the materials within it. Water strongly absorbs red wavelengths, while blue wavelengths penetrate farther. Phytoplankton pigments such as chlorophyll, suspended sediments, and dissolved organic matter also absorb and scatter light, changing the wavelengths that travel back towards the surface and are detected by satellites.

Consider that most satellite data have information on only a few of the infinite wavelength bands radiated by the ocean. How do scientists estimate the amount of chlorophyll in the water from satellite data?

Scientists estimate chlorophyll concentrations by measuring the radiance at specific wavelengths, particularly in the blue and green regions of the spectrum. Chlorophyll absorbs blue light strongly, so increasing phytoplankton concentration generally reduces the blue radiance relative to green. Scientists use the ratio between these wavelengths’ bands, after correcting for atmospheric interference, to estimate chlorophyll concentration in the ocean.

What are the two main competing processes in the formation of plankton thin layers?

The two main competing processes in the formation of plankton thin layers are stratification and mixing. Stratification stabilizes the water column and reduces vertical turbulence, allowing phytoplankton to accumulate in concentrated layers, mixing acts against stratification by redistributing phytoplankton throughout the water column.

By what process and in what way do spring and neap tides affect the dissolved oxygen concentrations at the bottom of an estuary?

Spring tides produce stronger tidal currents that increase vertical mixing and break down stratification, allowing oxygen rich surface water to reach the bottom of an estuary and increase Dissolved Oxygen concentration. During neap tides, weaker tidal currents reduce mixing and allow stratification to strengthen this limits oxygen replenishment at the bottom while respiration and decomposition continue consuming oxygen causing bottom water DO to decrease.

Describe how the mechanisms we covered in class create thin layers of phytoplankton concentrations

- phytoplankton thin layers form through several physical and biological mechanisms, including velocity shear, convergent swimming, buoyancy, gyrotactic trapping, situ growth, and intrusion. Velocity shear can stretch phytoplankton distributions into thinner layers, while convergent swimming causes organisms to accumulate at specific depths. Buoyancy can also create thin layers when sinking phytoplankton reach neutral buoyancy at the pycnocline and stops sinking. Additionally, phytoplankton may grow and accumulate in narrow regions where light and nutrient conditions are favorable. Strong stratification helps maintain these layers by reducing vertical mixing.

Explain the differences between the use of sound by toothed whales and baleen whales?

Toothed whales generally produce higher frequency sounds that travel shorter distances and use sound for both education and communication. Echolocation allows them to locate individual prey, such as fish and squid, by detecting returning echoes. Baleen whales generally produce lower frequency sounds that can travel much further underwater and primarily use sound for communication. Unlike toothed whales, Baleen whales do not use echolocation because their small planktonic prey are poor acoustic targets, and their low frequency sounds have wavelengths that are too long for detecting such small prey effectively

What organs/mechanisms do dolphins use to create and receive sound?

Dolphins generate outgoing sounds using vocal structures identified in the lecture as vocal cords. The sounds pass through the melon, which focuses them into directional beam. Returning echoes are received through the lower jaw and transmitted through a fatty channel to the ear. This allows dolphins to use echolocation to detect the location and characteristics of objects and prey.

Explain rods and cones, what they are used for, and how they are distributed in the human retina-

Rods and cones are photoreceptor cells in the human retina that detect light. Rods are highly sensitive to light and are responsible for black and white vision under low light conditions. They are primarily distributed in the peripheral retina. Cones require brighter light and are responsible for color vision. There are three types of cones that detect short, medium, and long wavelengths of light. Cones are concentrated in the fovea, where they provide sharp central vision.

What are the benefits and disadvantages of pinhole optics to organisms-

Pinhole optics allow light to pass through a small opening, producing a relatively sharp image without the need for lens. However, the small opening restricts the amount of light entering the eye, resulting in a dim image. Increasing the opening size would allow more light to enter but would also reduce image sharpness.

How does the use of a lens improve optics in an organism

- A lens improves optics by allowing more light to enter the eye while still producing a clear image. Unlike a pinhole which must restrict light to maintain sharpness, a lens refracts incoming light rays and focuses them onto a single point on the retina. This allows organisms to see more clearly under lower light conditions

Why do teleost fish have spherical lenses, compared to the thin lens that terrestrial organisms usually use?

Teleost fish have spherical lenses because light undergoes less refraction when traveling from water into the eye compared with light traveling from air into the eye. Since water and the cornea have similar refractive indices, the cornea provides little focusing power underwater. Aspherical lens provides greater refraction allowing fish to focus incoming light onto the retina and produce a clear image.

What competitive advantage do Karinia brevis have with regards to nutrient uptake?

Karenia brevis has a competitive advantage because it can obtain nutrients through multiple pathways allowing it to survive and grow in low nutrients environments where other phytoplankton may struggle. It also produces brevotoxins that can cause fish deaths. As the dead fish decompose, nutrients are released into the water, providing an additional nutrient source that helps sustain the bloom

Describe a typical K. brevis bloom scenario-

A typical karenia brevis bloom begins offshore in association with nitrogen fixing trichodesmium, which provides nutrients and favorable shaded conditions for growth. Because offshore waters have low silica concentrations, diatoms are limited in their ability to compete, allowing K. Brevis to become the dominant phytoplankton species. As the bloom develops, brevetoxins can cause fish kills and the decomposition of the dead fish release additional nutrients that help sustain and expand the bloom. Currents can then transport the bloom toward coastal water.

Give a general description of coastal upwelling and how it affects primary production

. Coastal upwelling occurs when wind causes surface water to move off shore through Ekman transport , allowing cold nutrient rich deep water to rise to the surface. These nutrients become available to phytoplankton in the sunlit portion of the water column, promoting photosynthesis and growth, As a result coastal upwelling generally increases primary production.

What is the main geostrophic current in the Gulf of Mexico?

The loop current is the main geostrophic current in the gulf of Mexico. It enters through the Yucatan channel circulates through the eastern gulf and exits through the Florida straits.

Describe how this current can affect K. brevis blooms in southwest Florida. Include a discussion of how onshore transport at bottom occurs.

The loop current and associated geostrophic circulation influences the transport and development of karenia brevis blooms along southwest Florida. Although the loop current generally remains offshore of the broad west Florida shelf, blooms can be transported toward the coast through local upwelling circulation or onshore bottom Ekman transport associated with geostrophic flow. These processes move offshore water containing K.Brevis toward shallower coastal waters, where favorable conditions and recycled nutrients from fish kills can help the bloom expand. However, when the loop current interacts with the shelf break nutrient rich deep water upwelling can also promote competing phytoplankton species, potentially limiting K, brevis dominance.