Resumo

CONTRERAS-ESPINOSA, Francisco; RIVERA-GUZMAN, Nadia E.  e  SEGURA-AGUILAR, Raquel. Nutrients and primary productivity on intermittent tropical coastal lagoon (La Mancha, Ver) Gulf of México. Hidrobiológica [online]. 2005, vol.15, n.3, pp.299-310. ISSN 0188-8897.

In the coastal lagoon of La Mancha, the effect of the sand barrier's opening implies that the lagoon loses along this period (157 days), 1'148,400 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 mgCm³hr: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 mgCm³hr:mg^-1m^-3).

Palavras-chave : Coastal lagoon; ephemeral lagoon; nutrients; primary productivity; Mexico.