Download ESCI 204 Final Exam: Marine Ecology Questions and Answers and more Exams Physics in PDF only on Docsity!
ESCI 204 Final Exam with Verified
Answers A+ Graded Questions with
Answers.
Why do zooplankton perform diel vertical migration? What are the implications of this migration on nutrient and carbon transport in the open ocean? - ✔✔Cue: Light levels
- Problem: Energetically costly, swimming away from food
- Why do it?
- Avoidance of visual predators (better hungry than dead)
- Other possibilities:
- Maintaining horizontal position *(observed in estuaries)
- Reducing metabolic rate for increased growth
- Avoiding U/V radiation What causes vertical zonation patterns of benthos on rocky intertidal shorelines? - ✔✔Biological stress- predation, competition Physical stress-
*Draw triangle diagram How might whale falls serve as stepping stones for the dispersal of hydrothermal vent organism larvae? - ✔✔chemosynthetic bacteria start at hydrothermal vents in the tube worms then they disperse and skip across whale skeletons until they find the next vent Why else are whale carcasses important to the deep sea? - ✔✔they serve as nutrients and food sources for life in the deep sea chemosynthetic bacteria, osedax, hagfish, sleeper sharks, etc. Why is deep‐sea benthic species diversity so high? - ✔✔Silt diversity What roles to microbes and viruses play in marine ecosystems? - ✔✔Viruses - Release nutrients from prey via cell lysis
- Nitrogen fixation - cyanobacteria
- Nitrification - bacteria and archaea
- Denitrification - bacteria and archaea
available but reduces supply of nutrients because stratification reduces mixing
- Gravity removes nutrients from the surface layer How are marine food webs structured? Compare the significance of bottom‐up versus top‐down processes. - ✔✔Bottom-up control: flow of energy and materials in food webs where primary producers control growth and regulation of higher trophic levels (Example: phytoplankton primary productivity is controlled by light levels, temperature, and nutrient concentration Therefore, these factors will determine phytoplankton biomass) Top-down control: food webs where the top predators control abundance and dynamics of lower trophic levels (Example: Sea otters eat sea urchins that eat kelp) Be able to answer questions about why fish communities and even great whales appear to be
structured from the bottom up. - ✔✔Spatial variation in fish yield correlates with phytoplankton biomass Temporal variation in climate (NAO) correlates with fish yield Areas of low productivity will be more susceptible to changes in fish abundance More chlorophyll measured= more fish abundance Great whales mostly eat zooplankton which eat phytoplankton discuss the extent to which top predatory fish can exert top‐down control on marine food webs. - ✔✔A: Adding fish reduces zooplankton, but not phytoplankton
- B: If you add nutrients, zooplankton drop and phytoplankton increase
- C&D: Nutrient addition more important
discuss how sea otters and Orca whales influence marine ecosystems. - ✔✔- Sea otters eat crab
- Crab eat invertebrates that graze on eelgrass epiphytes
- Epiphytes reduce eelgrass growth
- Otters, by eating crab, release mesograzers from predation, reducing epiphytes in increasing eelgrass biomass!
- Sea otters eat urchins that eat kelp, so without them kelp biomass decreases
- bladder kelp outcompetes bull kelp in the presence of otters (less grazers)
- bull kelp outcompetes bladder kelp in the absence of otters (more grazers such as urchins)
Bladder kelp: macrocystis integrifoilia Bull kelp: nereocystis luetkeana discuss how Orca whales influence marine ecosystems. - ✔✔The Orca - Otter - Kelp - Urchin Food Web
- After decades of recovery, sea otters in the Aleutian islands declined
- Evidence indicated Orcas were eating them.
- Change in Orca feeding likely due to declining seal abundance The otter‐urchin‐kelp cascade reversed!
- Can deplete local fish populations
- In Puget Sound, harbor seals pick up contaminants from the fish they eat (Ross et al. 2013) Sea lions: Sea lion diet, Alaska
- Sea lions eat a range of fish
- Eat salmon when available
- Conflict with people and with salmon recovery plans Sea lions in the Columbia River: Still eating salmon below Bonneville dam Walrus: Benthic‐feeder - loves clams Orcas: Residents eat chinook salmon while transients eat marine mammals
Manatees & dugongs: Eat seagrass (and sometimes associated invertebrates)
- only herbivorous marine mammals Manatees live in more Atlantic regions and more fresh water Dugongs live in Pacific ocean, exclusively coastal Explain the causes and consequences of global warming on marine ecosystems. - ✔✔Evidence that increased atmospheric CO2 is primarily due to fossil fuel combustion Greenhouse effect: the gradual increase in average global temperature caused by the absorption of infrared radiation from earth's surface by greenhouse gases in the atmosphere such as water vapor and CO The "greenhouse effect"1 — warming that results when the atmosphere traps heat radiating from Earth toward space. Certain gases in the atmosphere block heat from escaping. Effects of warming
Saturation state (omega) = [Ca 2+][CO3 2-]/ ksp At equilibrium: ksp= [Ca 2+][CO3 2-] Consequences:
- coral bleaching
- shelled organisms (mollusks, bivalves, urchins) have lower survival rates
- economic perspective: shellfish industry takes a blow due to low populations of shellfish Effects:
- Increased CO
- Reduces ocean pH
- Reduces CO32‐, increasing CaCO3 solubility
- Ocean acidification (+ temperature) linked to coral bleaching
- Dissolution and death of organisms with CaCO3 shells (food‐web disruption)
