Domain: Natural Science — Environmental Science
Target concept: Eutrophication of nitrogen and phosphorus

Video generation prompt: Two transparent tanks were filled with equal volumes of tap water. Nitrogen and phosphorus nutrient solution was added to the left tank, while the right tank remained blank. Equal amounts of green algae were introduced into both tanks. Time-lapse photography was conducted for 7 days to record how the left tank and the right tank changed relative to each other over that time.

Evaluation guide:
(i) Target concept: Eutrophication-driven differential algal proliferation under nutrient enrichment.
Minimum mechanism: Green algae require N/P to multiply; excess N/P in water accelerates division rate beyond grazing/predation capacity, leading to visible biomass accumulation (turbidity, surface scum), which must manifest *only* where nutrients are added, given identical initial algae inoculation and environmental conditions.
(ii)Storyline: Frame 0–1: Two empty transparent tanks placed adjacent in fixed frontal view. → Frame 2–3: Both tanks filled with clear water (identical meniscus, no bubbles). → Frame 4: Liquid nutrient solution visibly enters left tank (dropper/pipette tip visible, liquid stream distinct). → Frame 5: Green algae introduced simultaneously into both tanks (particulate suspension visible entering water column). → Frame 6–end: Time-lapse progression showing left tank gradually developing green turbidity/scum while right tank stays translucent; contrast strengthens over time; no external intervention or lighting shift occurs; entire sequence viewed from static frontal angle capturing full side-by-side field.

Manual:
Experimental Procedure
1. Place two identical transparent tanks side-by-side.
2. Fill both with equal volumes of tap water.
3. Add nitrogen-phosphorus nutrient solution to left tank only.
4. Introduce equal amounts of green algae into both tanks.
5. Record time-lapse video for 7 days.
Observation of Experimental Phenomena
Left tank develops dense greenish turbidity/scum; right tank remains mostly clear or lightly green.
Summary of Experimental Principles
Excess nitrogen and phosphorus cause eutrophication, accelerating green algae growth and forming algal blooms — a key indicator of aquatic ecosystem imbalance.

Prompt Grounding rubric:
level_1: Neither tank is shown as a clear see-through container, or only one tank appears in frame, or the two containers are stacked or far apart rather than placed next to each other for direct comparison; no nutrient solution is shown entering either tank; no green algae are introduced into either tank; the setup does not resemble two paired tanks being compared over time.
level_2: Both tanks are visible and see-through, but the comparison setup is broken in some way: the nutrient solution is added to the wrong tank or to both tanks, algae are added to only one tank instead of both, or there is nothing distinguishing which tank is which (no consistent left/right placement, no visible difference in treatment).
level_3: Both tanks are clear, filled with water, and positioned next to each other in a single fixed shot; the nutrient solution is shown entering only the left tank; green algae are shown entering both tanks; no other intervention (stirring, added light, removing a tank) happens to either tank; the identity of each tank (which one received nutrients) stays visually clear throughout.
level_4: Everything described for level 3 is present, and beyond that it is unambiguous on sight which tank received the nutrient solution (a visible stream or drip enters only the left tank, none enters the right), and algae visibly enter both tanks at essentially the same time, with no hand, label, or prop blocking either tank or breaking their side-by-side placement.
level_5: Everything described for level 4 is present, and the actions additionally unfold in the expected order with no reversal: both tanks are filled with visibly identical water first, the nutrient solution then goes into the left tank only, algae then go into both tanks around the same time, and only after that does the time-lapse progression begin.

Scientific and Causal Correctness rubric:
level_1: Neither tank shows any greening or clouding of its water over the week; or both tanks turn green/cloudy by the same amount; or the right (no-nutrient) tank turns green while the left (nutrient) tank stays clear. Any of these would contradict nutrient-driven algal growth.
level_2: Some greening appears, but it doesn't track the treatment correctly: only the right tank clouds up, or the water turns green before the nutrient solution or algae are ever added, or the color that develops is not a plausible algae green (e.g., red, brown, or blue with no explanation), or both tanks cloud up to the same visible degree despite one having no added nutrients.
level_3: Over the course of the time-lapse, the left tank visibly turns cloudier and greener than the right tank, which stays close to clear or only very faintly tinted; the color change is confined to the water itself (not a coating on the glass or sediment at the bottom); no greening appears before the algae have been introduced; the left tank's greening becomes visible only after both the nutrient solution and the algae are present.
level_4: Everything described for level 3 holds, and the gap between the two tanks keeps growing or at least holding steady rather than narrowing: the left tank keeps getting visibly greener and cloudier across the week while the right tank never catches up or intensifies to match it.
level_5: Everything described for level 4 holds, and the full cause-and-effect chain is visible without confound: the nutrient solution clearly goes in before any greening starts, algae are present in both tanks before either could bloom, the left tank's bloom becomes visible earlier and grows denser than anything in the right tank, and no other phenomenon (a white precipitate, fungal fuzz, or dye-like color bleed) could be mistaken for the algal bloom itself.

Spatiotemporal Consistency rubric:
level_1: One of the tanks suddenly appears in a different spot or at a different size than before, or a tank blinks out of view and back; the water suddenly changes from clear to fully green (or the reverse) between two consecutive moments with no transition; or the pair of tanks is no longer shown next to each other at some point in the video.
level_2: The two tanks stay in roughly the same place, but something breaks continuity: the nutrient solution or algae appear inside a tank with no visible entry (no dropper, no pour, no scattering motion), the green turbidity in the left tank jumps from faint to thick within a single visible step, or the spacing or relative size between the tanks changes noticeably partway through.
level_3: The two tanks remain in the same fixed positions and sizes throughout; the nutrient solution visibly enters the left tank through a stream or drops rather than appearing instantly; algae are seen dispersing into the water rather than materializing; the left tank's green turbidity thickens gradually from moment to moment, but one small slip occurs, such as a brief instant where a tank's edge looks slightly warped, or the water's greenish tint flickers in strength for a moment before settling back onto its gradual trend.
level_4: Everything described for level 3 holds, and the two tanks additionally keep the same distance and relative size to each other across the whole time-lapse, with nothing (hand, label, or object) blocking the view of either tank's water column at any point, and no sudden shift in camera perspective or framing between the recorded moments.
level_5: Everything described for level 4 holds, and every visible motion is additionally physically sensible: the nutrient solution flows downward into the left tank under gravity, the algae disperse through gentle mixing rather than floating unnaturally or exploding outward, and the left tank's green turbidity increases as a smooth, continuous progression across the week rather than jumping or stuttering between the sampled moments.