Nutrients and primary productivity on intermittent tropical coastal lagoon (La Mancha, Ver) Gulf of México

Abstract

In the coastal lagoon of La Mancha, the effect of the sand barriers opening implies that the lagoon loses along this period (157 days), 1148,400 m3 of their original volume; when the barrier closes, the increment of water toward the interior of the system is calculated in approximately 950, 400 m3 reaching 1 663, 200 m3 . When the lagoon remained communicated with the sea (from June 23 to November 25 , the measured parameters showed the following medians values: salinity 22.0 ups, disolved oxygen 3.33 ml/l, pH 7.3 units; the concentrations of ammonia 7.24 µM; nitrates plus nitrite 0.6 µM, while phosphates registered 8.66 µM; like consequence N:P ratio was below to 1 (0.78), this means P>N; chlorophyll a reach 11.30 mg/m3 and primary productivity quantities was low (29.84 mgC/m3 /h) this causes a drop in C:Chl ratio of 2.50 mgCm3 hr:mg-1m-3.

During the period when the lagoon is isolated, salinity showed a descent (16.5 ups), as same as the concentration of dissolved oxygen (2.58 ml/l); pH was lightly higher (7.58 units); the ammonia was 8.47 µM and was detected a slight increment in the nitrates plus nitrite (1.65 µM), contrarily there was a decrease in phosphates (5.73 µM), this cause that N:P ratio increased lightly to 1.77; chlorophyll a diminished to 3.04 mg/m3 , contrarily there was a significant increment of the primary productivity (158.63 mgC/m3 /h), the above-mentioned brought gets a greater value of the C:Chl ratio (28.09 mgCm3 hr:mg-1m-3).