TOEFL ITP Reading set 023
Reading Comprehension practice — read the passage and choose the best answer.
การหมุนเวียนน้ำทะเลเทอร์โมฮาลีนกับประมง
- Line numbers appear every 5 lines.
- Answer all 10 questions, then choose ตรวจคำตอบ to see the Thai translation, score summary, and explanation.
- Use Previous / Next to open the previous or next practice set.
Thermohaline circulation is the slow, deep movement of ocean
water driven by differences in temperature and salt content.
Cold, salty water sinks in polar seas and travels toward the
equator along the ocean floor, while warmer surface water
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drifts poleward to replace it. This conveyor-like loop helps
redistribute heat around the planet and carries dissolved
nutrients that support marine food webs. Without it, many
coastal fisheries would lose the nutrient pulses that feed
plankton and, in turn, the fish populations people harvest.
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Fisheries managers watch this circulation closely because
shifts in sinking and upwelling can move productive fishing
grounds across seasons. When deep water rises near
continental shelves, it can enrich surface layers with
nitrate and phosphate. Those nutrients fuel blooms of
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phytoplankton, which become food for zooplankton and small
forage fish. Commercial fleets that target sardines,
anchovies, or cod often follow these enriched zones. If
warming freshens polar surface water and reduces sinking,
the upward supply of nutrients may weaken, and catch rates
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can fall even when fishing effort stays the same.
Scientists also warn that a sluggish thermohaline loop may
alter migration routes. Some species follow temperature
bands and oxygen levels shaped by deep currents; when those
bands shift, spawning grounds may move farther from ports
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that communities have used for generations. That mismatch
raises fuel costs and can leave traditional fishers with
empty nets while distant fleets gain a clear advantage.
Policy responses include expanding satellite and buoy
networks that track salinity and temperature at depth,
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setting flexible quotas when nutrient indicators decline,
and protecting nursery habitats along shelves where
upwelling still occurs. International agreements matter
because one nation's overfishing can erase gains made by
neighbors when stocks straddle borders. Treating
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thermohaline health as shared infrastructure—like roads or
ports—may help keep coastal livelihoods viable as the
ocean's deep engine slowly changes under climate pressure.