Franco Banfi / Sea star (Hacelia attenuata) on coral covered with mucilage, a symptom of rising sea temperature, Vis Island, Croatia, Adriatic Sea, Mediterranean.

Nigel Cattlin / Tomato (Solanum lycopersicon) with blossom end rot, symptom of calcium deficiency, cultivated in glasshouse. Berkshire, England, UK. July.

Nigel Cattlin / Apple (Malus domestica) tree leaves with interveinal chlorosis, symptom of iron deficiency.

Nigel Cattlin / Apple (Malus domestica) branch with fruits and leaves. Leaves exhibiting interveinal chlorosis, symptom of iron deficiency.

Franco Banfi / Red gorgonian coral (Paramuricea clavata) covered with mucilage, a symptom of rising sea temperature, Ventimiglia, Italy, Ligurian Sea, Mediterranean.

Franco Banfi / Yellow gorgonian (Eunicella cavolini) covered with mucilage, a symptom of rising sea temperature, Punta Campanella Marine Reserve, Massa Lubrense, Italy, Tyrrhenian Sea, Mediterranean.

Franco Banfi / Red gorgonian coral (Paramuricea clavata) covered with mucilage, a symptom of rising sea temperature, Punta Campanella Marine Reserve, Massa Lubrense, Italy, Tyrrhenian Sea, Mediterranean.

Franco Banfi / Sea urchin (Sphaerechinus granularis) on coral covered with mucilage, a symptom of rising sea temperature, Vis Island, Croatia, Adriatic Sea, Mediterranean.

Franco Banfi / Yellow gorgonian (Eunicella cavolini) covered with mucilage, a symptom of rising sea temperature, Vis Island, Croatia, Adriatic Sea, Mediterranean.

Franco Banfi / Red gorgonian coral (Paramuricea clavata) covered in mucilage, a symptom of rising sea temperature, Punta Campanella Marine Reserve, Massa Lubrense, Italy, Tyrrhenian Sea, Mediterranean.

Nigel Cattlin / Early symptoms of False smut (Ustilaginoidea virens) on Rice (Oryza sativa) ears , Philippines.

Paul D Stewart / Woodcut illustration of the 'Monster of Krakow' was reported widely in the mid sixteenth century as a real occurence. It was seen by many protestants as a monstrous symptom of divine displeasure at th...