Marine Biology Exam 3

What is dispersal, and why is it important for marine organisms?

Dispersal is the movement of organisms, usually larvae or propagules, away from their birthplace to new locations where they can settle and grow. It is important because it promotes genetic mixing, reduces competition, allows colonization of new habitats, helps organisms avoid predators, and connects marine populations

What are the differences between long-distance and short-distance dispersal?

Long-distance dispersal allows larvae to travel far from their birthplace using ocean currents, increasing gene flow and colonization opportunities. Short-distance dispersal keeps larvae closer to parent populations, increasing local retention and survival in familiar habitats.

Compare brooders and broadcast spawners in terms of departure strategy and settlement timing.

Brooders retain larvae for part of development and usually release larger, more developed larvae that settle quickly. Broadcast spawners release eggs and sperm directly into the water column, producing larvae that often disperse farther and settle later.

What are planktotrophic and lecithotrophic larvae? What are their trade-offs?

Planktotrophic larvae feed on plankton while developing, allowing long dispersal distances but increasing exposure to predators. Lecithotrophic larvae rely on yolk supplied by the egg, allowing shorter development times and often higher survival, but usually shorter dispersal distances.

How do ocean currents and vertical migration influence dispersal?

Ocean currents transport larvae horizontally over large distances, while vertical migration allows larvae to move between water layers with different current speeds and directions, influencing where they eventually settle.

What is PLD (planktonic larval duration), and how does it relate to dispersal distance?

PLD is the amount of time larvae spend in the plankton before settlement. Longer PLD generally leads to greater dispersal distances because larvae remain exposed to ocean currents for longer periods.

What is natal homing, and how is it detected?

Natal homing is the ability of organisms to return to their birthplace to reproduce. It is detected using tagging studies, chemical signatures, genetics, and tracking technologies.

How do larvae choose where to settle? What are some environmental and biological settlement cues?

Larvae use environmental and biological cues such as substrate type, sound, chemical signals, water flow, biofilms, light, and the presence of other organisms to identify suitable settlement habitats.

How do biofilms, sound, substrate type, and hydrodynamics affect settlement?

Biofilms release chemical signals that encourage settlement. Reef sounds help larvae locate habitats. Substrate type determines attachment success, while hydrodynamics influence larval transport and the ability to remain attached after settlement

How does climate change (e.g., temperature, storms) influence dispersal and settlement?

Rising temperatures can shorten larval development time and alter dispersal distance. Increased storm activity can disrupt transport pathways, damage settlement habitats, and reduce recruitment success.

What is marine connectivity, and why is it important for conservation?

Marine connectivity refers to the exchange of organisms among populations through dispersal. It is important because connected populations are more resilient, maintain genetic diversity, and support recovery after disturbances.

What role do MPAs play in protecting dispersal corridors and settlement habitats?

Marine Protected Areas help conserve spawning grounds, dispersal pathways, and settlement habitats, allowing populations to reproduce successfully and replenish nearby ecosystems.

What are the major ways humans have historically exploited marine and estuarine fish populations?

Humans have exploited fisheries through large-scale harvesting, industrial fishing, trawling, overfishing, habitat destruction, and pollution.

What is overfishing, and what are some key case studies of fishery collapse?

Overfishing occurs when fish are harvested faster than populations can recover. Examples include the North Sea herring collapse, Atlantic cod decline, and Hudson River striped bass collapse.

What does it mean to “fish down the food web”?

Fishing down the food web means fisheries progressively target smaller and lower trophic-level species after larger top predators become depleted.

How do top predator losses affect ecosystems? Compare to bottom-up control.

Loss of top predators causes trophic cascades that alter prey abundance and ecosystem structure. Top-down control is driven by predators regulating lower trophic levels, while bottom-up control is driven by nutrient and resource availability affecting productivity.

How do habitat loss and pollution impact fisheries?

Habitat loss removes nursery grounds and spawning habitats, while pollution lowers water quality, disrupts food webs, and reduces fish survival and reproduction.

How did PCB pollution affect fish and people in the Hudson River?

PCB pollution contaminated fish tissues, making fish unsafe for consumption, harming fish health, and posing health risks to humans who consumed contaminated fish

What is the role of invasive species like zebra mussels in altering estuarine systems?

Zebra mussels alter food webs, outcompete native species, change nutrient cycling, and modify water clarity and ecosystem structure.

Are marine fish populations naturally stable, or are they mainly shaped by human impacts?

Marine fish populations naturally fluctuate because of environmental conditions and density-dependent regulation, but human activities such as overfishing and habitat destruction strongly shape modern population trends.

What are some common fishery management tools (e.g., quotas, MPAs, gear restrictions, seasonal closures)?

Common management tools include catch quotas, Marine Protected Areas, seasonal closures, gear restrictions, catch size limits, and protected nursery habitats.

What makes a fishery management plan effective?

Effective fishery management plans use scientific data, enforce regulations, protect habitats, monitor populations, and balance conservation with sustainable harvesting.

How can science-based conservation help maintain fish populations and ecosystem health?

Science-based conservation uses population monitoring, ecosystem management, habitat protection, and sustainable harvest limits to maintain biodiversity and fishery productivity

How optimistic are you that we can effectively manage fisheries and ecosystem health? And why?

Effective management is possible when science-based regulations, enforcement, habitat protection, and international cooperation are combined. Recovery examples such as North Sea herring demonstrate that fish populations can recover with proper management.