Guano deposits

Other sources of minable phosphorous included huge guano deposits created by the droppings of seabirds on rocky coastlines. Intensive mining led to the depletion of these deposits by the early 1900s. 

Organic N export from Fishing and Guano deposition ... 

POPs. For example, seabirds in the Arctic appear to be conveying Hg, HCBs, and DDT to their rookeries via guano deposition. Similarly, salmon contaminate upland streams following their death after spawning as their body burden of toxicants is eventually released to the terrestrial ecosystem. 

Most weathering processes, to be sure, take place in an environment where aerobic bacteria are active, unless there are considerable quantities of nitrogenous organic matter present. Anaerobic conditions, which usually also imply pH values close to (or less than) 7, are encountered in certain marine muds, guano deposits, and elsewhere. The anaerobe, Clostridium acidiurici (Liebert), which is known to occur in soils, produces ammonia, carbon dioxide and acetic acid from uric acid, guanine and xanthine (Baker and Beck, 1942), while Streptococcus allantoicus forms — in addition to ammonia and carbon dioxide — urea, oxamic acid, etc. Oxalic acid is a common product in the decomposition of guano. 

The above-mentioned organic acids may be expected to produce conditions in which silica of silicate minerals is dissolved, and — assuming the phosphate concentration is adequate or sufficient time has elapsed at lower concentrations — the silicate minerals become replaced by phosphate minerals. Although little is known concerning the conditions of oxidation vs. reduction encountered in guano deposits, such a mode of replacement must be attributed to the conversion of feldspar laths to variscite-metavariscite at Malpelo Island (McConnell, 1943). Indeed, the conditions may be aerobic at the surface, whereas anaerobic conditions obtain at the lower portions in contact with the country rock. 

A related theory was that the nitrates were remnants of ancient guano deposits (Gautier, 1894). Once again, there is much guano along the current coastline, but one objection to the theory is the heights at which... 

The answer had a name, Crookes told his audience nitrogen. Nitrogen fertilizer made it possible to grow more wheat on less land. Yet the planet s stores of nitrogen also were running low. The guano deposits were nearly exhausted. The nitrate mines of Chile were destined to be depleted within a few decades. 

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