Higher acidity in the ocean can impair the sensory systems of fish, particularly their ability to:
- Digest protein
- Swim faster
- Detect predators
- Generate scales
Explanation: Studies show that altered brain chemistry in acidified water can interfere with a fish's ability to smell or hear predators.
Which global network was established to standardize ocean acidification data and monitoring?
Explanation: The Global Ocean Acidification Observing Network (GOA-ON) coordinates international monitoring efforts and data sharing.
Which of these is a synergistic stressor that often acts alongside acidification to damage coral reefs?
- Tidal shifts
- Lower salinity
- Light intensity
- Thermal stress
Explanation: Ocean warming (thermal stress) and acidification act together, often leading to more frequent and severe coral bleaching.
Ocean acidification specifically makes it more difficult for organisms to maintain their:
- Swim speed
- Internal pH
- Blood volume
- Body weight
Explanation: Organisms must expend more energy to pump out excess hydrogen ions and maintain their internal acid-base balance.
Which non-calcifying organism can increase its growth rate under higher CO2 conditions?
- Fleshy algae
- Giant clams
- Sea urchins
- Hard corals
Explanation: Unlike calcifiers, many species of fleshy algae or 'seaweeds' grow faster with more dissolved CO2 available for photosynthesis.
Which 'natural laboratory' is used by scientists to study long-term acidification effects?
- Deep trenches
- Sandy bays
- Salt pans
- CO2 vents
Explanation: Volcanic CO2 vents naturally acidify surrounding water, allowing researchers to see how ecosystems adapt over generations.
Which historical event provides a geological analog for the current rate of ocean acidification?
- The Cambrian
- The Ice Age
- The Holocene
- The PETM
Explanation: The Paleocene-Eocene Thermal Maximum (PETM) involved a massive release of carbon and significant ocean acidification, though at a slower rate than today.
Calcifying organisms use carbonate ions to build shells and skeletons primarily made of:
- Magnesium oxide
- Sodium chloride
- Calcium carbonate
- Silica crystals
Explanation: Organisms like corals, mollusks, and some plankton combine calcium and carbonate ions to create calcium carbonate structures.
What is the primary reason the Southern Ocean is a 'hotspot' for acidification?
- Heavy shipping
- Volcanic activity
- Low salt levels
- High CO2 solubility
Explanation: CO2 dissolves better in the cold waters of the Southern Ocean, leading to faster decreases in carbonate saturation.
Pteropods, often called by this nickname, are tiny sea snails whose shells dissolve in acidified water:
- Sea angel
- Sea butterfly
- Marine slug
- Giant sea snail
Explanation: Pteropods are known as 'sea butterflies' due to their wing-like swimming appendages. They are a vital food source for many fish.
What is the primary impact of acidification on the 'Metabolic rate' of many marine invertebrates?
- Depression
- Stabilization
- Acceleration
- Fluctuation
Explanation: Maintaining internal acid-base balance requires more energy, which can lead to metabolic depression and slower growth rates.
Ocean acidification leads to a significant decrease in the concentration of which specific ion?
- Carbonate
- Sulfate
- Bicarbonate
- Hydroxide
Explanation: Increased hydrogen ions react with carbonate ions to form bicarbonate, thereby reducing the carbonate available for calcifying organisms.
Which 'G' in the Sustainable Development Goals (SDGs) includes a target (14.3) to minimize ocean acidification?
- SDG 14
- SDG 13
- SDG 7
- SDG 1
Explanation: SDG 14 ('Life Below Water') specifically targets the reduction of ocean acidification through enhanced scientific cooperation.
The pH scale used to measure ocean acidity is based on which mathematical relationship?
- Linear
- Logarithmic
- Geometric
- Exponential
Explanation: The pH scale is logarithmic, meaning a decrease of one pH unit represents a ten-fold increase in acidity (hydrogen ion concentration).
The 'Carbonate Compensation Depth' (CCD) is the depth at which the rate of carbonate rain equals the rate of:
- Deposition
- Dissolution
- Evaporation
- Freezing
Explanation: At the CCD, carbonate minerals dissolve as fast as they fall from above, leaving the seafloor below this depth free of carbonate ooze.
What happens to the availability of nutrients like iron and nitrogen in a more acidic ocean environment?
- Bioavailability shifts
- Remain constant
- Double instantly
- They disappear
Explanation: Changing pH can alter the chemical form of nutrients, potentially making them more or less available for uptake by marine life.
Which of the following describes the change in sound absorption in an acidic ocean?
- Frequency doubles
- Absorption decreases
- Remains constant
- Absorption increases
Explanation: Chemical changes in acidified water reduce the absorption of low-frequency sound, making the ocean 'noisier' as sound travels further.
Which of the following describes the 'Lysocline' in the context of ocean chemistry?
- Salinity changes
- Oxygen vanishes
- Dissolution starts
- Pressure peaks
Explanation: The lysocline is the depth at which the rate of calcium carbonate dissolution increases dramatically.
The ability of a marine organism to regulate its internal pH is known as:
- Photosynthesis
- Homeostasis
- Metabolism
- Osmosis
Explanation: Acid-base homeostasis is the physiological process of maintaining a stable internal pH despite external environmental changes.
Ocean acidification primarily affects the 'saturation state' of which mineral used by corals?
- Magnetite
- Feldspar
- Aragonite
- Hematite
Explanation: Corals specifically use the aragonite form of calcium carbonate, which is more sensitive to pH drops than calcite.
Which Greek letter is used to represent the saturation state of calcium carbonate minerals in seawater?
Explanation: Omega (Ί) is the symbol for the saturation state; values below 1.0 indicate that the water is corrosive to calcium carbonate.
Which shell-forming organism is the primary consumer at the base of the Southern Ocean food web?
- Pteropods
- Leopard seals
- Blue whales
- Tuna fish
Explanation: Pteropods (sea butterflies) are a key food source for fish and birds; their shells are highly sensitive to acidification.
Despite the term 'acidification', the current global average pH of the ocean indicates it is still:
- Slightly acidic
- Highly acidic
- Purely neutral
- Slightly basic
Explanation: The ocean's pH has dropped from about 8.2 to 8.1. Since it is above 7.0, it remains basic (alkaline), but is moving toward the acidic side.
Which type of 'Blue Carbon' ecosystem can serve as a localized refuge from ocean acidification?
- Sandy beaches
- Open gyres
- Deep trenches
- Seagrass meadows
Explanation: Seagrasses remove CO2 through photosynthesis, creating localized areas of higher pH during the day.
Which process describes the natural movement of CO2 from the surface to the deep ocean via biological activity?
- Tidal wave
- Jet stream
- Biological pump
- Upwelling flow
Explanation: The biological pump transports carbon to the deep sea, where it eventually contributes to deep-water acidification.
In the chemical equation of acidification, hydrogen ions react with carbonate to produce which substance?
- Sulfate
- Methane
- Hydroxyl
- Bicarbonate
Explanation: H+ + CO3(2-) -> HCO3-. This reaction 'consumes' the carbonate ions that calcifiers need.
Since the start of the Industrial Revolution, the acidity of the ocean's surface waters has increased by approximately:
- Five percent
- Sixty percent
- Ten percent
- Thirty percent
Explanation: The drop of 0.1 pH units since the pre-industrial era represents a roughly 30% increase in hydrogen ion concentration.
The 'saturation horizon' is the depth in the ocean below which calcium carbonate structures begin to:
- Crystallize
- Expand
- Solidify
- Dissolve
Explanation: Below the saturation horizon (Ί < 1), seawater is undersaturated, causing calcium carbonate shells to dissolve.
Colder waters, such as those in the Arctic, are more vulnerable to acidification because they:
- Have less salt
- Lack marine life
- Flow much faster
- Absorb more CO2
Explanation: Gases like CO2 dissolve more readily in cold water than in warm water, leading to faster acidification in polar regions.
The depth of the aragonite saturation horizon is generally ______ in the Pacific than in the Atlantic.
- Shallower
- Identical
- Unstable
- Deeper
Explanation: Because Pacific waters are 'older' and have accumulated more CO2 from respiration, the corrosive waters are closer to the surface.
Which biological process in the ocean naturally helps to temporarily mitigate local acidity in seagrass beds?
- Photosynthesis
- Upwelling
- Respiration
- Decomposition
Explanation: During photosynthesis, plants and algae consume CO2, which can locally raise the pH and provide a temporary buffer for nearby organisms.
What is the primary acid formed when seawater reacts with atmospheric carbon dioxide?
- Nitric acid
- Hydrochloric
- Carbonic acid
- Sulfuric acid
Explanation: CO2 + H2O forms H2CO3, which is carbonic acid. This then dissociates into hydrogen ions and bicarbonate.
Indian scientists monitor ocean acidification trends primarily through which organization?
Explanation: The Indian National Centre for Ocean Information Services (INCOIS) tracks various oceanographic parameters including carbon data.
As ocean acidification increases, the concentration of hydrogen ions in the water does what?
- Stabilizes
- Increases
- Decreases
- Fluctuates
Explanation: Acidification is defined by the increase in hydrogen ion (H+) concentration, which results in a lower pH value.
Ocean acidification is often referred to as global warming's 'evil ______'.
- Twin
- Sibling
- Partner
- Shadow
Explanation: Because both are caused by rising CO2 levels, ocean acidification is frequently called the 'evil twin' of climate change.
Which specific factor measures the ocean's resistance to atmospheric CO2 absorption?
- Hadley cell
- Coriolis force
- Revelle factor
- Albedo effect
Explanation: The Revelle factor relates the change in atmospheric CO2 to the change in total dissolved inorganic carbon; a higher factor means lower buffering capacity.
In coastal areas, acidification can be worsened by which process involving land runoff?
- Desalination
- Sedimentation
- Subduction
- Eutrophication
Explanation: Nutrient runoff causes algal blooms; when these die and decompose, CO2 is released, further lowering the pH of coastal waters.
What is the primary indicator of ocean acidification used in global climate reports?
- Salinity
- Wave height
- Ice thickness
- Surface pH
Explanation: The decline in average global surface ocean pH is the standard metric used to track the progress of acidification.
Ocean acidification is expected to impact corals most directly by reducing their rate of:
- Respiration
- Calcification
- Reproduction
- Photosynthesis
Explanation: Corals require a high saturation of carbonate to build their stony skeletons; lower pH makes this process energetically difficult.
What percentage of human-generated carbon dioxide emissions has the ocean absorbed since the Industrial Revolution?
- Thirty percent
- Eighty percent
- Ten percent
- Fifty percent
Explanation: The ocean acts as a massive carbon sink, absorbing approximately 30% of the CO2 released into the atmosphere by human activities.
The interaction of acidification with 'Hypoxia' (low oxygen) creates which type of effect on marine life?
- Synergistic
- Antagonistic
- Neutral
- Additive
Explanation: Acidification and hypoxia often occur together and their combined stress is worse than the sum of their individual impacts.
Calcification rates in the world's oceans are projected to decline by how much by 2100 under high-emission scenarios?
- Only 5%
- 50 to 80%
- Over 95%
- 10 to 30%
Explanation: Scientific models suggest a significant reduction in calcification across coral reefs and plankton communities by the end of the century.
Which form of calcium carbonate is more soluble and therefore more susceptible to ocean acidification?
- Dolomite
- Calcite
- Aragonite
- Halite
Explanation: Aragonite is a more soluble crystal form of calcium carbonate than calcite, making organisms that use it (like corals) more vulnerable.
Which specific chemical species acts as the 'buffer' against rapid pH changes in seawater?
- Phosphate
- Borate
- Silicate
- Nitrate
Explanation: While the carbonate system is the primary buffer, the borate system provides significant additional buffering capacity in the ocean.
Which gas is the primary driver of the ongoing process of ocean acidification?
- Carbon dioxide
- Sulfur dioxide
- Nitrous oxide
- Methane gas
Explanation: When the ocean absorbs CO2 from the atmosphere, it reacts with seawater to form carbonic acid, leading to acidification.
The Revelle Factor is highest in which part of the ocean?
- Polar regions
- Deep trenches
- Sub-tropics
- Equator
Explanation: Higher Revelle factors in polar regions indicate that these waters have the lowest capacity to buffer further CO2 increases.
How does ocean acidification influence the toxicity of certain metals like copper in seawater?
- Decreases toxicity
- Removes metals
- Increases toxicity
- Creates metals
Explanation: Lower pH can change the chemical form of metals, often increasing the concentration of free ions which are more toxic to marine life.
Which of these acts as the ultimate 'long-term' buffer for ocean acidity over thousands of years?
- Seafloor sediment
- River flow
- Cloud cover
- Wind speed
Explanation: Over long timescales, the dissolution of calcium carbonate sediments on the seafloor will help neutralize the added acidity.
Which region's fisheries are currently most affected by 'corrosive' upwelling waters?
- Red Sea
- Persian Gulf
- Dead Sea
- US West Coast
Explanation: The Pacific Northwest has seen significant oyster hatchery failures due to the upwelling of naturally CO2-rich, acidified water.
Which form of calcium carbonate is typically used by mollusks like oysters and mussels?
- Calcite
- Quartz
- Gypsum
- Aragonite
Explanation: Many mollusks use aragonite for their shells, making their larval stages especially vulnerable to acidic conditions.
Which chemical 'equilibrium' is shifted when CO2 is added to seawater?
- Water cycle
- Oxygen balance
- Nitrogen cycle
- Carbonate system
Explanation: Adding CO2 shifts the balance between dissolved CO2, carbonic acid, bicarbonate, and carbonate ions.
The chemical process of acidification leads to an increase in which dissolved carbon species?
- Graphite
- Anthracite
- Carbonate
- Bicarbonate
Explanation: As carbonate is consumed by hydrogen ions, the concentration of bicarbonate ions increases.
Acidification can cause fish otoliths to grow abnormally. What are otoliths?
- Gill covers
- Scaly layers
- Tail fins
- Ear stones
Explanation: Otoliths are small calcium carbonate structures in the inner ear of fish used for balance and orientation.
In a more acidic ocean, the bioavailability of which essential micronutrient for phytoplankton might change?
- Sodium
- Iron
- Calcium
- Potassium
Explanation: Changes in pH alter the chemical speciation of iron, potentially making it harder for phytoplankton to absorb it.
The 'Saturation Horizon' has been moving in which direction as a result of acidification?
- Upward
- Downward
- Deepward
- Sideways
Explanation: As the ocean acidifies, the depth at which carbonate minerals dissolve (the saturation horizon) becomes shallower.
Which of the following organisms might actually benefit from higher CO2 levels in the ocean?
- Clams
- Seagrasses
- Starfish
- Oysters
Explanation: Non-calcifying photosynthetic organisms like seagrasses can benefit from higher CO2 concentrations for growth.
Which of these is a major socio-economic risk of ocean acidification?
- Fishery collapse
- Soil erosion
- Urban smog
- Forest fires
Explanation: Acidification threatens the foundation of the marine food web and coral reef habitats, risking the livelihoods of millions dependent on fishing.
Which type of microscopic plankton is particularly vulnerable to acidification due to its calcium carbonate plates?
- Dinoflagellates
- Cyanobacteria
- Coccolithophores
- Diatoms
Explanation: Coccolithophores are single-celled algae that surround themselves with calcium carbonate scales (coccoliths).
Ocean acidification can lead to 'Hypercapnia' in fish. What is hypercapnia?
- Low oxygen
- Scaly skin
- Rapid swimming
- High blood CO2
Explanation: Hypercapnia is the buildup of carbon dioxide in the blood or body fluids, which can impair physiological functions.
The 'buffering capacity' of the ocean refers to its ability to resist changes in:
- Salinity
- pH
- Pressure
- Temperature
Explanation: The ocean has a natural chemical system that resists changes in pH, but this capacity is being overwhelmed by the speed of CO2 absorption.