Ocean warming is the rise in sea temperatures caused mainly by increased greenhouse gases (like CO2 and CH4) trapping more heat in the atmosphere; that extra heat is absorbed by the oceans (EK STB-4.G.1). Effects include thermal expansion (sea level rise), more frequent marine heatwaves, decreased oxygen solubility (worse coastal hypoxia), shifts in species ranges, altered metabolic and reproductive rates, kelp declines, and coral bleaching from loss of zooxanthellae—some corals recover, others die (EK STB-4.G.2–3; keywords: sea surface temperature rise, coral bleaching, zooxanthellae loss). On the AP exam, expect questions connecting greenhouse-gas increases to ocean impacts and human/ecosystem consequences (Unit 9 weighting). For a focused review, see the Topic 9.6 study guide (https://library.fiveable.me/ap-environmental-science/unit-9/ocean-warming/study-guide/jkfHigqMY9PbkfE51027) and more unit resources (https://library.fiveable.me/ap-environmental-science/unit-9). Practice with the AP-style problems at (https://library.fiveable.me/practice/ap-environmental-science).

Greenhouse gases (like CO2, CH4, N2O) trap more outgoing infrared radiation in the atmosphere, so Earth’s surface and the air warm. Much of that extra heat is absorbed by the oceans (about 90% of excess heat), raising sea surface temperatures. Warmer water expands (thermal expansion), contributing to sea level rise, and holds less dissolved oxygen, which can create coastal hypoxia. Higher temperatures also push species toward the poles, change metabolic and reproductive rates, and cause marine heatwaves that stress corals—leading to zooxanthellae loss and coral bleaching (some corals recover, some die). On the AP exam, link the greenhouse-gas → increased atmospheric heat → ocean warming chain and mention effects like thermal expansion, coral bleaching, altered metabolic rates, and range shifts (CED STB-4.G.1–3). For a focused recap, check the Topic 9.6 study guide on Fiveable (https://library.fiveable.me/ap-environmental-science/unit-9/ocean-warming/study-guide/jkfHigqMY9PbkfE51027) and practice related questions at Fiveable (https://library.fiveable.me/practice/ap-environmental-science).

Ocean warming (driven by rising greenhouse gases) affects marine animals and fish in lots of important ways. Warmer water raises metabolic rates so fish need more food and oxygen, but oxygen solubility decreases as temperature rises—creating stress and expanding coastal hypoxia zones. Species shift toward the poles or deeper water (range shifts), changing community interactions and fisheries. Reproductive timing and success can change (some species spawn earlier or produce fewer offspring). Marine heatwaves and kelp-forest declines remove habitat for many species. Coral bleaching happens when corals lose their symbiotic algae (zooxanthellae); repeated bleaching can cause coral mortality and reef collapse. These are all CED concepts (STB-4.G: habitat loss, metabolic/reproductive changes, coral bleaching). This topic commonly appears on Unit 9 multiple-choice and FRQ prompts, so review the Ocean Warming study guide (https://library.fiveable.me/ap-environmental-science/unit-9/ocean-warming/study-guide/jkfHigqMY9PbkfE51027) and more Unit 9 materials (https://library.fiveable.me/ap-environmental-science/unit-9). Practice questions are also available (https://library.fiveable.me/practice/ap-environmental-science).

Coral bleaching is a specific stress response: when ocean warming (driven by increased greenhouse gases) raises sea temperatures, corals expel their symbiotic algae (zooxanthellae). That loss makes corals turn white and reduces their main energy source—some corals recover if temperatures drop and algae return, but prolonged bleaching leads to starvation and higher mortality (EK STB-4.G.1–3; keywords: zooxanthellae loss, coral recovery). “Regular” coral death describes the end result (tissue loss and dead calcium-carbonate skeleton exposed). Death can follow severe or repeated bleaching, but corals also die from disease, pollution, physical damage, or ocean acidification. So bleaching = reversible stress sign (early warning); death = permanent loss of live coral and habitat (coral mortality). For AP review, this is covered under Topic 9.6 (ocean warming)—see the study guide (https://library.fiveable.me/ap-environmental-science/unit-9/ocean-warming/study-guide/jkfHigqMY9PbkfE51027) and extra practice (https://library.fiveable.me/practice/ap-environmental-science).

Corals and algae have a close, mutual relationship: tiny photosynthetic algae (zooxanthellae) live inside coral tissues and provide most of the coral’s energy (through photosynthesis), while the coral supplies the algae with shelter and nutrients. When ocean warming (driven by rising greenhouse gases, EK STB-4.G.1) stresses corals—especially during marine heatwaves—zooxanthellae are expelled or lose pigments. That loss turns corals white (coral bleaching, STB-4.G.3). Some corals can recover if temperatures drop soon enough and algae recolonize; others starve and die if warming persists. Ocean warming also changes metabolic and reproductive rates and forces species range shifts (STB-4.G.2). For AP exam prep, know the cause (greenhouse-gas-driven sea surface temp rise), the mechanism (zooxanthellae loss), and outcomes (bleaching, possible recovery vs. mortality). For a concise review, see the Topic 9.6 study guide (https://library.fiveable.me/ap-environmental-science/unit-9/ocean-warming/study-guide/jkfHigqMY9PbkfE51027), the unit overview (https://library.fiveable.me/ap-environmental-science/unit-9), and practice questions (https://library.fiveable.me/practice/ap-environmental-science).

Corals bleach when heat stress makes them expel their symbiotic algae (zooxanthellae). Whether a coral recovers or dies depends on several AP-relevant factors: severity and duration of the marine heatwave (short, mild warming → more chance of recovery); species and genotype (some coral species and some zooxanthellae strains tolerate higher temperatures); the coral’s energy reserves and health going into the event; local stressors like pollution, sedimentation, or disease that reduce resilience; and frequency of repeat bleaching (repeated events lower recovery odds). Recovery happens if zooxanthellae return before the coral’s energy stores run out; mortality happens when stress is too long/intense or additional stressors prevent recolonization. This links directly to EK STB-4.G.2–3 (ocean warming → coral bleaching, variable outcomes). For more AP-aligned review, see the Topic 9.6 study guide on Fiveable (https://library.fiveable.me/ap-environmental-science/unit-9/ocean-warming/study-guide/jkfHigqMY9PbkfE51027) and try practice questions (https://library.fiveable.me/practice/ap-environmental-science).

When ocean temps get too high, fish and other marine animals can’t just “tough it out.” Warmer water causes loss of habitat (e.g., kelp and cold-water zones shrink), makes oxygen less soluble (so less O2 available), and raises metabolic rates—which increases oxygen demand and stress. Reproduction and development often change (timing shifts, lower survival of eggs/larvae), and many species shift their ranges toward the poles to find cooler water. Extreme warming also contributes to marine heatwaves and coral bleaching (loss of zooxanthellae), which destroys reef habitat that lots of fish depend on. These effects are listed in the AP CED under EK STB-4.G.1–3 and are tested in Unit 9 (global change). For a focused review on ocean warming and coral bleaching, see the Topic 9.6 study guide (https://library.fiveable.me/ap-environmental-science/unit-9/ocean-warming/study-guide/jkfHigqMY9PbkfE51027). For broader Unit 9 review and extra practice, check the unit page (https://library.fiveable.me/ap-environmental-science/unit-9) and the practice problems (https://library.fiveable.me/practice/ap-environmental-science).

Ocean warming shifts where marine species can live by changing temperature, oxygen, and habitat availability. As sea surface temps rise (greenhouse-gas driven; CED EK STB-4.G.1), many species move toward the poles or to deeper, cooler water—so you’ll see range shifts and local gains or losses of species. Warming also lowers oxygen solubility and increases metabolism, so organisms need more oxygen but get less, stressing fish and invertebrates. Reproduction and timing can change (altered reproductive timing, sex ratios), and habitats like kelp forests and coral reefs decline—coral bleaching happens when zooxanthellae are lost (STB-4.G.2–3). For AP exam answers, use CED terms: sea surface temperature rise, marine heatwaves, species range shifts, decreased oxygen solubility, coral bleaching. For a focused review, see the Topic 9.6 study guide (https://library.fiveable.me/ap-environmental-science/unit-9/ocean-warming/study-guide/jkfHigqMY9PbkfE51027) and try practice questions (https://library.fiveable.me/practice/ap-environmental-science).

Warmer water speeds up ectotherm metabolism: biochemical reactions generally follow a Q10 ~2, so metabolic rates roughly double for every 10°C rise. That raises oxygen and energy demands (higher respiration, faster food intake) while warmer water holds less dissolved O2 and can worsen coastal hypoxia—a double stress. Increased metabolism can also shift growth, reproduction and timing (earlier spawning, altered sex ratios in some species) and raise vulnerability to disease. These changes match the CED idea of “altered metabolic rates” and links to decreased oxygen solubility and coastal hypoxia (STB-4.G.2). For AP study, remember coral bleaching is a separate but related effect (loss of zooxanthellae; STB-4.G.3). For a focused review, see the Topic 9.6 study guide (https://library.fiveable.me/ap-environmental-science/unit-9/ocean-warming/study-guide/jkfHigqMY9PbkfE51027) or the Unit 9 overview (https://library.fiveable.me/ap-environmental-science/unit-9). For extra practice, use Fiveable’s APES practice problems (https://library.fiveable.me/practice/ap-environmental-science).

Yes—ocean warming can definitely affect marine reproduction. Warmer water changes metabolic rates, which can shift the timing of spawning (phenology), reduce gamete production, and alter larval development and survival. For some species (e.g., certain fish and turtles), temperature even influences sex ratios during development, so warmer conditions can skew populations. Increased metabolic demand plus lower oxygen solubility and more frequent marine heatwaves can lower reproductive success and cause range shifts as adults move toward cooler waters. Coral reproduction is especially vulnerable: bleaching (loss of zooxanthellae) reduces energy for gamete production and can lower coral recruitment and recovery (CED EK STB-4.G.2; STB-4.G.3 keywords: coral bleaching, zooxanthellae loss, altered metabolic rates, reproductive timing shifts). This topic shows up on APES free-response prompts about effects of warming, so review the Ocean Warming study guide (https://library.fiveable.me/ap-environmental-science/unit-9/ocean-warming/study-guide/jkfHigqMY9PbkfE51027) and Unit 9 overview (https://library.fiveable.me/ap-environmental-science/unit-9). For extra practice, check the APES question bank (https://library.fiveable.me/practice/ap-environmental-science).

Coral turns white during bleaching because it loses the colorful symbiotic algae called zooxanthellae (or their pigments). Those algae live inside coral tissues, provide most of the coral’s food via photosynthesis, and give corals their brown/yellow/green colors. When ocean temperatures rise (driven by greenhouse-gas–forced ocean warming; EK STB-4.G.1), the stress causes corals to expel or lose those algae. With the algae gone, the coral’s translucent tissue reveals the white calcium-carbonate skeleton underneath, so it looks “bleached.” If stressful conditions persist, the coral can starve and die; if temperatures return to normal soon enough, some corals can regain zooxanthellae and recover (STB-4.G.3). For AP review, this links directly to ocean warming effects on species and coral mortality—see the Topic 9.6 study guide (https://library.fiveable.me/ap-environmental-science/unit-9/ocean-warming/study-guide/jkfHigqMY9PbkfE51027) and the Unit 9 overview (https://library.fiveable.me/ap-environmental-science/unit-9). For extra practice, check Fiveable’s APES problems (https://library.fiveable.me/practice/ap-environmental-science).

Climate change warms the ocean because extra greenhouse gases trap more heat, raising sea surface temperatures and causing marine heatwaves (EK STB-4.G.1). Corals live in a narrow temp range and have symbiotic algae (zooxanthellae) that provide food. When water gets too warm, corals expel those algae—that’s coral bleaching (STB-4.G.3). Bleached corals turn white; some recover if conditions improve, but prolonged or repeated warming leads to coral mortality, loss of habitat, reduced biodiversity, and weakened reef structure. Warming also changes metabolic and reproductive rates and can push reef species poleward (STB-4.G.2). On the AP exam, you should be able to explain the greenhouse-gas cause, describe bleaching (zooxanthellae loss), and list ecological effects. For a quick topic review check Fiveable’s Ocean Warming study guide (https://library.fiveable.me/ap-environmental-science/unit-9/ocean-warming/study-guide/jkfHigqMY9PbkfE51027) and practice questions (https://library.fiveable.me/practice/ap-environmental-science) to prep.

Scientists track ocean temperature change using several complementary methods. For sea-surface temperature (SST) they use satellites that measure radiated heat (good global coverage, used to calculate SST anomalies and marine heatwaves). For subsurface temps and ocean heat content (OHC) they use in-situ instruments: drifting and fixed buoys (including the Argo float network), ship-based sensors and expendable probes (XBTs), and long-term oceanographic cruises. Argo floats profile temperature (and salinity) down to ~2,000 m; Deep Argo reaches greater depths. Scientists combine these records into global datasets and integrate temperature over depth to get OHC—a key metric because most excess heat from greenhouse-gas forcing goes into the ocean (thermal expansion and sea level rise follow). These datasets let you analyze trends, anomalies, and impacts like coral bleaching and species range shifts—exactly the kind of data-analysis practice APES expects. For topic review, see the Ocean Warming study guide (https://library.fiveable.me/ap-environmental-science/unit-9/ocean-warming/study-guide/jkfHigqMY9PbkfE51027) and more practice problems (https://library.fiveable.me/practice/ap-environmental-science).

Greenhouse gases (GHGs) trap outgoing infrared (longwave) radiation from Earth—that’s the greenhouse effect. More GHGs means less heat escapes to space, so the atmosphere warms. That warmer air then transfers heat to the ocean by conduction (air touching the surface), convection (wind-driven mixing), and by reducing nighttime/seasonal heat loss from the surface. The ocean also absorbs most incoming solar radiation directly at the surface, and with a warmer atmosphere less heat is lost, so sea surface temperatures rise (EK STB-4.G.1). Warmer water holds less dissolved oxygen, changes metabolic and reproductive rates of organisms, drives species poleward, and causes coral bleaching when zooxanthellae are expelled (STB-4.G.2–3). This is a classic AP Global Change concept you should be ready to explain on free-response questions. For a focused review, see the Topic 9.6 study guide (https://library.fiveable.me/ap-environmental-science/unit-9/ocean-warming/study-guide/jkfHigqMY9PbkfE51027) and more unit resources (https://library.fiveable.me/ap-environmental-science/unit-9); practice problems are at (https://library.fiveable.me/practice/ap-environmental-science).

Short answer: lots of marine species are already being hurt by warmer oceans—here are concrete examples tied to the CED keywords. - Corals (Great Barrier Reef): repeated marine heatwaves have caused mass coral bleaching when corals expel their zooxanthellae; big bleaching events occurred in 2016–2017, with many corals dying (coral bleaching, zooxanthellae loss, coral mortality). - Kelp forests (giant kelp): heatwaves and warmer waters let herbivores like purple sea urchins explode and overgraze kelp, causing kelp forest decline. - Fish range shifts: species like Atlantic cod and mackerel are moving poleward as sea surface temperatures rise (species range shifts). - Salmon and other cold-water species: warmer coastal and river temperatures alter metabolic rates and reproductive timing and can increase mortality. - Oxygen-sensitive organisms: warmer water holds less O2, worsening coastal hypoxia zones and stressing benthic life (decreased oxygen solubility, coastal hypoxia). For more AP-aligned details, see the Topic 9.6 study guide (https://library.fiveable.me/ap-environmental-science/unit-9/ocean-warming/study-guide/jkfHigqMY9PbkfE51027). Practice related questions at (https://library.fiveable.me/practice/ap-environmental-science).