Question: which group of organisms is most commonly responsible for red tides
[{'answer': 'dinoflagellates', 'provenance': [{'wikipedia_id': '25448', 'title': 'Red tide', 'start_paragraph_id': 1, 'start_character': 149, 'end_paragraph_id': 1, 'end_character': 164, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]