Question: what is the main source of nutrients in an estuary
[{'answer': 'detritus', 'provenance': [{'wikipedia_id': '78471', 'title': 'Estuary', 'start_paragraph_id': 40, 'start_character': 114, 'end_paragraph_id': 40, 'end_character': 122, 'bleu_score': 1.0, 'section': 'Section::::Implications for marine life.\n'}]}, {'answer': 'sea water', 'provenance': [{'wikipedia_id': '78471', 'title': 'Estuary', 'start_paragraph_id': 6, 'start_character': 370, 'end_paragraph_id': 6, 'end_character': 379, 'bleu_score': 1.0, 'section': 'Section::::Definition.\n'}]}, {'answer': 'fresh water', 'provenance': [{'wikipedia_id': '78471', 'title': 'Estuary', 'start_paragraph_id': 2, 'start_character': 227, 'end_paragraph_id': 2, 'end_character': 238, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'The mixing of sea water and fresh water'}, {'provenance': [{'wikipedia_id': '78471', 'title': 'Estuary', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 0, 'bleu_score': 1.0, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5491924536679727309}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '78471', 'title': 'Estuary', 'start_paragraph_id': 40, 'start_character': 0, 'end_paragraph_id': 40, 'end_character': 163, 'bleu_score': 0.9243880458347601, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5491924536679727309}, 'section': 'Section::::Implications for marine life.\n'}]}, {'provenance': [{'wikipedia_id': '78471', 'title': 'Estuary', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 439, 'bleu_score': 0.923732788176137, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5491924536679727309}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '40059080', 'title': 'Freshwater inflow', 'section': 'Section::::Estuaries.\n', 'start_paragraph_id': 4, 'end_paragraph_id': 4, 'meta': {'evidence_span': ['Estuarine ecosystems need freshwater inflow to maintain their productivity, or to continue to produce biomass.', 'The low-salinity conditions of the marine water are created when freshwater mixes with the saltwater of the estuarine system. Average [salinity] for freshwater is around 0.5 parts per thousand (ppt) whereas average salinity of the ocean is 35 ppt. The salinity will not be consistent throughout a particular estuary and will be differ from one estuary to the next but its level will range from 0.5 ppt to 35 ppt. In estuaries, primary producers take up nutrients such as nitrogen and phosphorus.']}}]}, {'provenance': [{'wikipedia_id': '78471', 'title': 'Estuary', 'section': 'Section::::Abstract.', 'start_paragraph_id': 2, 'end_paragraph_id': 2, 'meta': {'evidence_span': ['The mixing of seawater and fresh water provide high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world.', 'Estuaries form a transition zone between river environments and maritime environments. They are subject both to marine influencessuch as tides, waves, and the influx of saline waterand to riverine influencessuch as flows of fresh water and sediment.']}}]}]