OCN 150 Exam 4 chapters

Class Information Before Break

Next class will not meet as per the announcement from the department, as it coincides with the Thanksgiving holiday. This is an opportunity for students to prepare for their upcoming assessments and assignments over the break.
This will be the final class before the Thanksgiving break, setting the stage for final reviews and preparations.
An extra points assignment will be available on Canvas to incentivize student engagement and provide additional opportunities for grade improvement.
- Opens: Monday at 9 AM
- Closes: December 2 at 11:59 PM
- Submission details will be provided when the assignment opens to ensure clarity on requirements.
If you have any questions regarding the materials or upcoming assignments, feel free to ask during office hours or through email.

Exam 4:
- Date: December 6
- Time: 8 AM (NOT 9 AM) - it is crucial to note the time change to avoid confusion.
Homework:
- Due: December 5 at 11:59 PM - please ensure that all submissions adhere strictly to the deadline to avoid penalties.
A review session has been scheduled to help students prepare:
- Date: December 5
- Time: 12:15 PM
- Location: DePaulo Hall 1056 - attendance might be beneficial for reinforcing concepts before the exam.
An email will be sent with reminders before the break to help keep students on track.

Plankton serve as the primary producers in aquatic ecosystems; their extensive biomass reinforces their role in food webs and nutrient cycling, although high biomass can lead to toxin production as a side effect.

Ciguatera Toxin:
- Bioaccumulates in shellfish and fish, primarily affecting those who consume these contaminated organisms.
- Symptoms can lead to gastrointestinal and neurological disorders but are typically not fatal.
Domoic Acid:
- Found primarily in marine diatoms and is more prevalent in colder climates.
- Similar effects as Ciguatera, it poses health risks to humans and can also lead to significant die-off of marine life due to its toxic impact.

Observed as a pea-green scum in lakes, which is indicative of severe nutrient overload, leading to ecological imbalances.
Nutrient enrichment results in cultural eutrophication, where excess nutrients accelerate algal growth, disrupting aquatic environments.

Description: Areas with depleted dissolved oxygen, typically caused by algal blooms and subsequent bacterial decomposition. These are particularly significant in places like the Gulf of Mexico, where nutrient runoff from the Mississippi River exacerbates the issue.
Result in mass mortality of marine organisms such as fish and shrimp, severely affecting local fisheries and ecosystems.
Global Marine Dead Zones:
- Maps show high concentrations near coastlines and urban areas where nutrients are higher, indicating a growing environmental challenge.

In a typical marine environment, nutrient concentrations fluctuate with depth due to photosynthesis and decomposition processes.
Higher nutrient availability occurs deeper in the water column after phytoplankton die off, as decomposition replenishes nutrients critical for various marine life forms.

Temperature decreases with depth, and surface waters are well-mixed due to currents, affecting the distribution of marine organisms.
Light intensity significantly decreases with depth, resulting in variable phytoplankton distribution depending on available light resources.

Chlorophyll a Concentration:
- Maximum concentrations can occur at depth rather than the surface due to phytoplankton adaptation strategies which allow them to utilize light more effectively at various depths.
- After the chlorophyll maximum, degradation processes release nutrients back into the water column, supporting ongoing productivity.

Polar Regions:
- Experienced intensive spring blooms fueled by seasonal light changes, with constant nutrient availability supporting high productivity levels throughout the year.
Temperate Zones:
- Characterized by seasonal productivity, with distinct spring and fall blooms influenced by nutrient cycles and light availability leading to fluctuating marine life.
Tropical Regions:
- Even though warm temperatures prevail, nutrient limitations often prevent significant primary producer blooms despite the high light availability, creating unique ecological challenges.

Primary producers form the foundational base of marine food webs, crucial for sustaining diverse marine life and their ecosystems.
Coastal and nearshore areas play a critical role as fish nursery habitats, facilitating the growth and survival of juvenile fish and supporting diverse marine populations.

Overfishing remains a significant concern, necessitating careful regional management of fish stocks to prevent collapse.
Keystone species serve as indicators of ecosystem health; declining populations often signal broader ecological issues that require attention.
Importance of implementing sustainable fishing practices to ensure a continued food source for future generations.

Sustainability cards issued by institutions like Scripps and the Monterey Bay Aquarium assist consumers in making informed choices regarding seafood consumption.
- Fish are categorized into best choices (green), moderate (yellow), and those to avoid (red), aiding in efforts to maintain healthy fish stocks and protect marine ecosystems.