EigoPro 準1級 読解 — The Acidifying Ocean

When we speak of carbon dioxide, the conversation almost invariably drifts skyward—to warming air, retreating glaciers, and rising seas. Yet the ocean has quietly absorbed roughly a third of the carbon dioxide that human activity has released since the dawn of industry, and it has paid a chemical price for this service. As the gas dissolves in seawater, it forms carbonic acid, nudging the ocean toward the acidic end of the pH scale. The shift sounds modest—surface waters are about thirty per cent more acidic than they were two centuries ago—but in chemistry, small numbers on a logarithmic scale conceal enormous changes. The organisms most immediately imperilled are those that build shells and skeletons from calcium carbonate: corals, oysters, certain plankton, and the tiny sea snails known as pteropods. Acidified water is corrosive to these structures, dissolving them faster than the creatures can rebuild. Because pteropods and similar plankton sit near the base of the marine food web, their decline threatens to ripple upward, depriving fish, whales, and ultimately the fishing communities that depend on them. What begins as an invisible chemical adjustment thus propagates into an economic and humanitarian concern. Some commentators take refuge in the ocean's vastness, assuming that so immense a body of water can buffer any insult indefinitely. This complacency is misplaced. The very capacity that has shielded the atmosphere is finite, and as it erodes, the ocean will absorb less carbon, accelerating the warming it once restrained. The acidifying ocean is therefore not a separate crisis but the submerged half of the same one. To treat it as a footnote to the climate story is to misread the chemistry on which much of life depends.

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この単元の問題を3問、解説つきで公開しています

準1級 · 読解 · 全5問

問 1

What is the main idea of the passage?

  • The ocean's vast size allows it to neutralize carbon dioxide indefinitely without lasting harm.
  • Ocean acidification is an under-recognized but integral part of the carbon crisis that endangers marine life and the people who rely on it.
  • Coral reefs are the only marine organisms genuinely threatened by chemical change in the sea.
  • Rising air temperatures pose a far greater danger to humanity than any change in seawater.
Phrase

The acidifying ocean is therefore not a separate crisis but the submerged half of the same one.

準1級読解海洋科学主旨把握
⚡ひとことで

本文は「海洋酸性化は気候危機の見落とされた一部で、海洋生物と人間を脅かす」という論旨。

選択肢の解説Choice Analysis

「Ocean acidification is an under-recognized but integral part of the carbon crisis that endangers marine life and the people who rely on it.」

正解

本文は (1) CO2 の議論は空ばかりに向くが海も3分の1を吸収し化学的代償を払う→ (2) 炭酸カルシウムの殻を持つ生物が溶け食物網を通じ漁業まで波及→ (3) 海の緩衝力は有限で、酸性化は気候危機の『水面下の半身』だ、と展開する。よって『見落とされがちだが炭素危機に不可分で、海洋生物とそれに依存する人々を脅かす』が主旨。

  • 「The ocean's vast size allows it to neutralize all carbon dioxide indefinitely and without any lasting harm to marine life.」

    = 海は広大なので無限に中和できる ━ 本文は第3段でこの考えを『complacency is misplaced (慢心は見当違い)』と明確に否定している。

  • 「Rising air temperatures pose a far greater danger」

    = 気温上昇の方がはるかに危険 ━ 本文は気温と酸性化を『同じ危機の半身』と同格に扱い、優劣はつけていない。

  • 「Coral reefs are the only marine organisms genuinely threatened」

    = 脅かされるのはサンゴ礁だけ ━ 本文は coral に加え oysters・plankton・pteropods を挙げており『サンゴだけ』ではない。

▦Collocation
パターン意味例
pay a price for ~~の代償を払うIt paid a chemical price for this service.
drift skyward空の方へ流れるThe conversation drifts skyward.
ripple upward上方へ波及するThe decline ripples upward.
the submerged half of ~~の水面下の半身the submerged half of the same crisis
misread the chemistry化学を読み違えるTo treat it as a footnote is to misread the chemistry.
❝例文

  • The ocean has absorbed roughly a third of human carbon emissions.

    海は人間の炭素排出の約3分の1を吸収してきた。

  • What begins as a chemical shift propagates into an economic concern.

    化学的変化として始まったものが経済的懸念へと波及する。

  • Acidification is not a separate crisis but part of the same one.

    酸性化は別個の危機ではなく同じ危機の一部だ。

💡Tip · 覚えるコツ

主旨設問は最終段の結論文 (not A but B 構文) を探すと速い。本文は『not a separate crisis but the submerged half』で全体を一言に集約している。

問 2

According to the passage, what happens chemically when carbon dioxide dissolves in seawater?

  • It forms carbonic acid, pushing the ocean toward the acidic end of the pH scale.
  • It combines with calcium carbonate to strengthen marine shells.
  • It raises the ocean's pH, making the water more alkaline.
  • It evaporates back into the atmosphere, leaving the water unchanged.
Phrase

As the gas dissolves in seawater, it forms carbonic acid, nudging the ocean toward the acidic end of the pH scale.

準1級読解海洋科学詳細把握
⚡ひとことで

CO2 が海水に溶けると炭酸を生成し、pH を酸性側へ押しやる。

選択肢の解説Choice Analysis

「It forms carbonic acid, pushing the ocean toward the acidic end of the pH scale.」

正解

第1段で『As the gas dissolves in seawater, it forms carbonic acid, nudging the ocean toward the acidic end of the pH scale』と明記される。nudge を push に言い換えた『炭酸を生成し、海を pH スケールの酸性側へ押しやる』が正解。

  • 「It evaporates back into the atmosphere」

    = 大気へ蒸発して戻る ━ 本文は溶けて炭酸になると述べており蒸発しない。逆の記述。

  • 「It combines with calcium carbonate to strengthen marine shells」

    = 炭酸カルシウムと結合し殻を強化 ━ 酸性水は殻を『溶かす (corrosive)』のであり強化はしない。正反対。

  • 「It raises the ocean's pH, making the water more alkaline」

    = pH を上げてアルカリ性にする ━ 酸性化なので pH は下がる。方向が逆。

▦Collocation
パターン意味例
dissolve in ~~に溶けるThe gas dissolves in seawater.
form carbonic acid炭酸を生成するIt forms carbonic acid.
nudge toward ~~の方へ押しやるnudging the ocean toward acidity
the pH scalepHスケールthe acidic end of the pH scale
on a logarithmic scale対数スケールでsmall numbers on a logarithmic scale
❝例文

  • Carbon dioxide dissolves in seawater and forms carbonic acid.

    二酸化炭素は海水に溶けて炭酸を生成する。

  • The reaction nudges the water toward the acidic end of the scale.

    その反応は水をスケールの酸性側へ押しやる。

  • Surface waters are about thirty per cent more acidic than two centuries ago.

    表層水は2世紀前より約30%酸性度が高い。

💡Tip · 覚えるコツ

詳細設問は本文の動詞を同義語に置換した肢が正解 (nudge→push)。pH の『酸性化＝pH低下』と『アルカリ性＝pH上昇』の方向を取り違える誤答に注意。

問 3

Why does the decline of pteropods matter beyond the organisms themselves?

  • They directly absorb the majority of the carbon dioxide released by industry.
  • They are the primary source of carbonic acid in the ocean.
  • They are the only creatures capable of rebuilding calcium carbonate shells.
  • They sit near the base of the marine food web, so their loss ripples upward to fish, whales, and fishing communities.
Phrase

Because pteropods and similar plankton sit near the base of the marine food web, their decline threatens to ripple upward

準1級読解海洋科学詳細把握
⚡ひとことで

翼足類は食物網の底辺にいるため、減少が上位の魚・クジラ・漁業へ波及する。

選択肢の解説Choice Analysis

「They sit near the base of the marine food web, so their loss ripples upward to fish, whales, and fishing communities.」

正解

第2段で『pteropods and similar plankton sit near the base of the marine food web, their decline threatens to ripple upward, depriving fish, whales, and ultimately the fishing communities』と述べる。食物網の底辺ゆえ減少が上位へ波及するという因果を言い換えた肢が正解。

  • 「They are by far the primary source of all the carbonic acid found in the ocean.」

    = 炭酸の主要な発生源 ━ 炭酸は CO2 と海水の反応で生じる。翼足類が発生源とは述べていない。

  • 「They are the only creatures that are capable of rebuilding any calcium carbonate shells.」

    = 殻を再生できる唯一の生物 ━ コルや牡蠣も炭酸カルシウムの殻を作る。『唯一』は言い過ぎ。

  • 「They directly absorb the great majority of all the carbon dioxide that industry releases into the air each year.」

    = CO2 の大半を直接吸収する ━ CO2 を吸収するのは海全体。翼足類が大半を吸収するとは述べていない。

▦Collocation
パターン意味例
the base of the food web食物網の底辺near the base of the marine food web
ripple upward上方へ波及するTheir decline ripples upward.
deprive ~ of ...~から…を奪うdepriving fish of food
depend on ~~に依存するcommunities that depend on them
threaten to V~する恐れがあるthreatens to ripple upward
❝例文

  • Pteropods sit near the base of the marine food web.

    翼足類は海洋食物網の底辺近くにいる。

  • Their decline threatens to ripple upward to whales and fisheries.

    彼らの減少はクジラや漁業まで波及する恐れがある。

  • Many coastal communities depend on these fish stocks.

    多くの沿岸地域はこれらの魚資源に依存している。

💡Tip · 覚えるコツ

『なぜ重要か』設問は理由節 (Because ...) と結果動詞 (ripple upward / depriving) を探す。『only / primary / majority』を含む肢は言い過ぎの典型誤答。

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