Question

Marine algae along the west coast of North America do not increase in species richness toward the tropics but peak at about 70 species per \(100 \mathrm{km}\) of coastline around \(40^{\circ} \mathrm{N}\) latitude (Gaines and Lubchenco 1982 ). Along the east coast of North America, species richness gradually increases as you move toward the tropics. Discuss why these patterns might hold.

Short answer

West coast richness is influenced by cold currents and nutrient upwelling, while the east coast shows increased richness towards the tropics due to warmer temperatures and stable conditions.

Step-by-step solution

Understanding Species Richness Patterns

Species richness refers to the number of different species represented in an ecological community. On the west coast of North America, species richness of marine algae peaks around 40°N and does not increase towards the tropics, contrasting with the east coast, where richness increases as one moves south.

Consider Climate and Ocean Currents

The west coast's unique pattern is influenced by cold ocean currents, such as the California Current, and upwelling that brings nutrient-rich waters to the surface, supporting diverse algae communities around 40°N latitude. These currents maintain a temperate climate suitable for many species.

Examine Temperature and Latitude Effects

On the east coast, warmer temperatures closer to the tropics support higher marine biodiversity. As the latitude decreases moving southwards, both water and air temperatures increase, leading to more suitable habitats for a wider range of algae species.

Analyze Historical Biogeography

Historical factors, such as glaciation events and sea level changes, especially on the east coast, may have allowed for periods of isolation and dispersal which affect present-day species richness. This can lead to a gradual increase in species moving toward the tropics where conditions have historically been stable.

Key concepts

Marine Algae

Marine algae, essential players in ocean ecosystems, display intriguing patterns of species richness. These patterns are vital in understanding ecological diversity. Marine algae, or seaweeds, contribute significantly to underwater habitats by providing food and shelter. They range in size from tiny phytoplankton to large seaweeds like kelp. Their distribution is crucial to understanding algae biodiversity.
On the west coast of North America, marine algae species richness intriguingly peaks around 40°N latitude. Despite moving towards the tropics, the number of different species does not increase. This stands in stark contrast to other regions, where warmer waters typically harbor more diverse marine life.

• The peak at 40°N is atypical, caused by environmental factors that are unique to this area rather than warmer tropical regions.
• These factors include specific climate conditions and ocean currents that benefit marine algae communities.

Understanding these patterns helps ecologists predict changes in biodiversity as climates and oceanic conditions evolve.

Climate and Ocean Currents

Climate and ocean currents play a critical role in shaping the biodiversity of marine algae along coastlines. On the west coast of North America, the California Current is a cold ocean current that significantly influences species richness patterns.
Cold currents, like the California Current, bring nutrient-rich waters from the ocean depths to the surface, a process known as upwelling.

• This upwelling supplies essential nutrients to marine algae, sustaining a diverse and rich ecosystem of algae species at around 40°N latitude.
• The temperate climate maintained by these currents creates suitable living conditions for numerous algae species, even in regions away from the tropics.

Contrastingly, the east coast experiences different current patterns that impact species richness differently, linking closely to climate influences.

Temperature and Latitude

Temperature and latitude are crucial in determining the variety and distribution of marine algae. As a general rule, increases in temperature usually support higher biodiversity, a pattern often observed in marine environments moving towards the tropics.
On the east coast of North America, as latitude decreases towards the equator, temperatures in both marine and terrestrial environments rise.

• This increase in temperature creates a more hospitable environment, supporting greater species richness and diversity within marine algae communities.
• Warm tropical waters especially foster diverse ecosystems by providing optimal growth conditions.

Understanding the relationship between temperature, latitude, and species richness helps explain the diverse patterns seen in different coastal regions.

Historical Biogeography

Historical biogeography looks at the past distribution of species and ecosystems to provide insights into current biodiversity patterns. This concept helps explain why certain areas might have richer species diversity today.
The east coast of North America, for example, has experienced various historical events that shaped its current biodiversity. Glaciation events and sea level changes have historically isolated and reconnected populations.

• Periods of isolation can promote speciation, creating new species and adding to biodiversity as populations adapt to unique conditions.
• Connections of previously isolated regions during sea level rise allowed species to disperse, increasing diversity in areas like the tropics where conditions are stable.

These historical processes lay the foundation for the varied patterns of species richness observed today across different latitudes.