Explore the changing color of the water in San Francisco Bay, with insights from a biologist on factors like light interaction and particles. Learn about the challenges in detecting long-term trends and the natural cycle of water turning green due to photoplankton populations. Join in on a trivia game and find out about a live jazz event at KQED headquarters.
Water in the bay appears greener due to increased phytoplankton abundance from shifting ecological dynamics.
Changes in clam populations have triggered a trophic cascade, impacting phytoplankton growth and bay water color.
Deep dives
The Color of the Bay: Green Waters and Anthropogenic Influences
The bay's water color has shifted over time from blue to green as observed by residents like Justin Hartung, with particular changes noted near Emeryville. Jim Cloran, a biologist with extensive experience studying the bay, explains that water color is influenced by light absorption, with non-living clay particles and microscopic algae (phytoplankton) contributing to the green hue through various sources like erosion and runoff. Data collected since 1968 shows an increasing trend of phytoplankton abundance, leading to greener bay waters, partly attributed to reduced sediment input and shifts in the biological communities.
Trophic Cascade: Clam Eaters, Phytoplankton Blooms, and Water Clarity
Changes in clam populations in the bay have set off a trophic cascade effect, resulting in increased phytoplankton due to fewer clams filtering them. The shift in seasonal phytoplankton patterns, including autumn blooms, started around 1999, coinciding with reduced clam numbers and elevated crab, flatfish, and shrimp populations. The increase in potential clam predators has disrupted the ecological balance, leading to the bay's greener waters through complex interactions within the food web.
Natural Climate Oscillations: Understanding the Current Greening Trend
The greening of the bay's waters since 1998 is not solely due to human-induced climate change but rather linked to natural climate oscillations affecting phytoplankton abundance. Strong winds causing coastal upwelling and nutrient-rich cold water have boosted biological productivity, supporting the growth of marine organisms that impact water clarity. Continued data collection is essential to monitor long-term changes and unravel the intricate relationships between climatic shifts, species dynamics, and water color variations.
Bay Curious listener Justin Hartung grew up here, and remembers the waters of the bay being more blue than they are today. He wonders: Is the bay getting greener? Bay Curious producer Amanda Font gives us the answer, and takes us into the science behind it.
This story was reported by Amanda Font. Bay Curious is made by Olivia Allen-Price, Katrina Schwartz, and Christopher Beale. Additional support from César Saldaña, Jen Chien, Katie Sprenger, Maha Sanad, Jasmine Garnett, Carly Severn, Joshua Ling, Holly Kernan and the whole KQED family.
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