Y09W38PA - What Ocean Acidification Means for Marine Life

This week you wrote an informative piece explaining what ocean acidification means for marine life. Now you'll read another student's piece and judge how strong it is. Working through how assessors evaluate informative writing sharpens your own approach.

Part 1

The Assessor Scorecard for

Informative – Informative piece

Informative writing conveys knowledge. It is objective, logically organised, and uses precise vocabulary so readers understand both the information and why it matters.

Ideas & Content

Ideas come from source material, but how you synthesise them determines quality. Identify what's most relevant and understand how ideas connect. Convey both the facts and the significance of those facts. Strong informative writing helps readers see the shape of the system, not just isolated details.

  • Relevant synthesis: selects and connects scientific information into a coherent explanation.

Structure & Cohesion

Informative structure is logical and purposeful. Move through information in an order that builds understanding — overview to detail, or simple to complex. Cohesion comes from signposting. Help readers see how each idea connects to what came before and what comes next.

  • Purposeful order: builds understanding from overview to causes and effects.

Audience & Purpose

Your purpose is to help readers understand a specific system or process. Your audience expects clarity and relevance — information structured so they can grasp how things work. You're writing for readers who want to know, not for readers who already know.

  • System understanding: helps readers grasp process and significance, not isolated facts.

Language Choices

Informative language is precise and accessible. Use domain-specific vocabulary where necessary, but explain unfamiliar terms. Choose words that convey exact meaning. Sentences are controlled but not rigid — vary enough to keep readers engaged.

  • Precise accessibility: explains scientific terms clearly and accurately.

Conventions

Conventions in informative writing serve clarity. Accurate grammar, spelling and punctuation allow your information to come through without distraction. Consistency in tense and perspective helps readers follow complex ideas.

  • Conventional clarity: keeps readers focused on the marine science, not errors.

Part 2

Today’s Marking Targets

Task in one sentence

Write a three-paragraph informative piece explaining what ocean acidification is, what causes it and what it means for marine ecosystems.

Let’s Focus

Three strands matter most this week: Ideas & Content, Language Choices and Structure & Cohesion. Ideas decide whether readers grasp significance, not just facts. Language decides whether scientific terms distinguish cause from effect. Structure decides whether the chain from process to consequence reveals itself.

Ideas & Content

When ideas are strong, you select the most important information and understand why it matters. You explain not just what happens but why it's significant. You help readers see that ocean acidification isn't a remote scientific issue — it affects the food chains marine ecosystems depend on.

What markers scan for

  • Clear explanation of what ocean acidification is and the chemical process involved.
  • Explanation of what it means for specific marine organisms and ecosystems.
  • Understanding of why the issue matters beyond isolated facts.

Score Bands

  • Basic

    Lists facts about acidification; limited explanation of why it matters.

  • Strong

    Explains the process and its effects; shows connection between cause and consequence.

  • Excellent

    Helps readers understand the significance of the issue for marine life.

Language Choices

Strong informative language is precise without being technical. Use domain vocabulary like pH, carbonic acid and calcium carbonate where necessary, and use it in context so readers understand. Choose words that distinguish between the cause (human CO2 emissions) and the effect (lowered pH).

What markers scan for

  • Domain vocabulary used accurately and in context.
  • Words that distinguish between cause, process and consequence.
  • Technical language that serves understanding rather than displaying knowledge.

Score Bands

  • Basic

    Language is clear but imprecise; scientific terms used loosely.

  • Strong

    Accurate vocabulary; clear distinctions between cause and effect.

  • Excellent

    Technical language serves understanding; explanations integrate terminology naturally.

Structure & Cohesion

Structure moves readers through information systematically. You might define ocean acidification first, then explain the cause, then show the consequences. Cohesion comes from signposting — making explicit how each idea follows from the last.

What markers scan for

  • Logical order that helps readers follow the chain of cause and consequence.
  • Clear transitions showing how ideas connect.
  • Structure that itself reveals how the system works.

Score Bands

  • Basic

    Information is accurate but order seems random.

  • Strong

    Clear progression from definition through cause to consequence.

  • Excellent

    Structure itself teaches — the order reveals how the system works.

Now read · Student sample

What Ocean Acidification Means for Marine Life

Year 9 sample · \~250 words

Student sample for assessment

Written by a Year 9 student in Perth, Western Australia, Australia.

Ocean acidification is the process by which the ocean becomes less alkaline—more acidic—as it absorbs carbon dioxide from the atmosphere. When CO2 dissolves in seawater, it forms carbonic acid, which lowers the ocean's pH. Scientists measure this by comparing pH levels over time. Before industrialisation, the ocean's pH was approximately 8.2, but it has since fallen to 8.1. Although this seems like a small change, it represents a 26 per cent increase in acidity, demonstrating how even tiny shifts in pH can have significant effects on marine chemistry. This acidification is caused primarily by human activities. The ocean absorbs approximately 25 to 30 per cent of the carbon dioxide that humans emit through burning fossil fuels, manufacturing and agriculture. As human CO2 emissions have increased dramatically since the Industrial Revolution, so has the amount of CO2 the ocean absorbs. The ocean acts as a carbon sink, absorbing excess CO2 that would otherwise accumulate in the atmosphere. While this absorption slows atmospheric climate change, it comes at a cost to ocean chemistry and the organisms that depend on it. Ocean acidification directly harms marine organisms that build shells and skeletons from calcium carbonate, including oysters, mussels, corals and certain types of plankton. As the ocean becomes more acidic, it becomes harder for these organisms to form and maintain their calcium carbonate structures. This is particularly devastating for coral reefs, which support approximately 25 per cent of all marine species. Coral reefs have already experienced multiple mass bleaching events due to warming waters, and acidification adds another stress. When foundational species like plankton and corals are threatened, entire ecosystems collapse, affecting fish populations and the food chains that depend on them.