Investigação de depósito de espículas de esponjas de água doce em um lago cárstico no Brasil

Machado, V. S.; Volkmer-Ribeiro, C.; Iannuzzi, R.

doi:10.1590/1519-6984.09814

V. S. Machado ^**e-mail: biologavsm@gmail.com

Programa de Pós-graduação em Geociências, Instituto de Geociências, Universidade Federal do Rio Grande do Sul – UFRGS, Av. Bento Gonçalves, 9500, Prédio 43113, CEP 91501-970, Porto Alegre, RS, Brazil

C. Volkmer-Ribeiro

Museu de Ciências Naturais – MCN, Fundação Zoobotânica do Rio Grande do Sul – FZB, CP 1188, CEP 90001-970, Rua Dr. Salvador França, 1427, CEP 90690-000, Porto Alegre, RS, Brazil

R. Iannuzzi

Departamento de Paleontologia e Estratigrafia, Instituto de Geociências, Universidade Federal do Rio Grande do Sul – UFRGS, Av. Bento Gonçalves, 9500, Prédio 43113, CEP 91501-970, Porto Alegre, RS, Brazil

*e-mail: biologavsm@gmail.com

Figuras (3)
Tabelas (2)

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Figure 1
On the left, map showing the localization the Serra Negra Lake, in Minas Gerais, Brazil and at central, satellite image showing the lake and the distinct sampling stations (St.): St. 1, Bebedouro Stream; St. 2, Small basins; St. 3, Margin near the macrophyte stands; St. 4, Channel formed close to the lake outlet; St. 5, Small depositional basin downstream the lake outlet; St. 6-10, Central portion of the lake covered with free water. The dashed line indicates the lake borders, and the thinner line indicates the borders of the free water surface. The arrows indicate the water flow in the lake.

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Figure 2
Optical Microscope pictures of the spicules of the six species of sponges found in the sediments of the Serra Negra Lake. a. megascleres, b. microscleres (Dosilia pydanieliVolkmer-Ribeiro, 1992VOLKMER-RIBEIRO, C., 1992. The freshwater sponges in some peat-bog ponds in Brazil. Amazoniana, vol. 12, no. 2, pp. 317-335.); c. gemmosclere (Metania spinata (Carter, 1881)); d. gemmosclere (Trochospongilla variabilis Bonetto and Ezcurra de Drago, 1973); e. gemmosclere (Radiospongilla amazonensis Volkmer-Ribeiro and Maciel, 1983); f. megasclere, g. long gemmosclere, h. short gemmosclere (Heterorotula fistulaVolkmer-Ribeiro and Motta, 1995VOLKMER-RIBEIRO, C. and MOTTA, J.F.M., 1995. Esponjas formadoras de espongilitos em lagoas no Triângulo Mineiro e adjacências, com indicação de preservação de habitat. Biociências, vol. 3, no. 2, pp. 145-169.).

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Figure 3
Graph showing the variation of the physical and chemical parameters at Stations 1-5 (St.) in Serra Negra Lake and streams during the two studied periods (Cond.: Conductivity (uS); pH: Hydrogen potential; Turbid.: Turbidity (U.N.T.); Silica: Dissolved silica (mg/L); Alkal.: Alkalinity (mg/L); DO: Dissolved oxygen (mg/L); BDO: Biochemical oxygen demand (mg/L); Temp.: Temperature (°C); Phosp.: Phosphorus (mg/L); AmmNitrog.: Ammoniacal nitrogen (mg/L); OrgNitrog.: Organic nitrogen (mg/L); Depth (m)).

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Table 1
Location and description of the sampling stations (St.) in the Serra Negra Lake and respective streams, Patrocínio, MG, are presented together with the results of the analysis of preservation conditions of the spicules, their relative total amount, their taxonomic identification and the relative amount of each spicule category in the sampled sediments.

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Table 2
Physical and chemical parameters of water of Serra Negra Lake, Patrocínio, MG, sampled during the two seasonal periods at the five sampling stations (St.).

St.	Description	Relative amount and preservation conditions of the spicules	Taxonomic analysis and relative quantification of each spicule category
1	Bebedouro stream. Channel with unidirectional little flow, dammed close to the lake and with scarce macrophytic vegetation. Dark-coloured sediment with fine granulometry.	Rare, incipiently formed and fragmented spicules	-
2	Southern part of the lake. Small basin of anthropic excavations with free water. Dark-coloured sediment with fine granulometry.	Rare, incipiently formed and fragmented spicules	-
3	Marginal point located in the central/northern part of the lake. Area formed by small basins and channels and covered with aquatic vegetation, which surrounds a deeper area with free water surface. Dark-coloured sediment with fine granulometry.	Abundant, completely formed and entire spicules	D. pydanieli: m (+ + +); mi (+ + +); gm (+) M. spinata: am (+ + +); bm (+ +); mi (+ +); gm (+) T. variabilis: m (+ + +); gm (+) R. amazonensis: m (+ + +); gm (+) H. fistula: m (+ + +); lgm (+); sgm (+)
4	Channel at the northern border, taking to the lake outlet. Dark-coloured sediment with large amount of sand and presence of millimetric to centimetric clasts.	Few, completely formed and entire spicules	D. pydanieli: m (+ +); mi (+ +) M. spinata: am (+ +); mi (+ +) R. amazonensis: m (+ + +); gm (+)
5	Microbasin of sedimentation formed along the course of the stream of the outlet of the lake. Dark-coloured sediment with great amount of sand. Presence of millimetric to centimetric clasts.	Few, completely formed, but fragmented spicules	O. navicella: m (+ +); gm (+)
6-10	Central/northern portion of the Serra Negra Lake, with larger area of free water. Black sediments with gelatinous aspect and presence of vegetal fragments still not decomposed.	Abundant, completely formed and entire spicules	D. pydanieli: m (+ + +); mi (+ + +); gm (+) M. spinata: am (+ + +); bm (+ +); mi (+ +); gm (+) T. variabilis: m (+ + +); gm (+) R. amazonensis: m (+ + +); gm (+) H. fistula: m (+ + +); lgm (+); sgm (+)

Parameters	June/2011 (high water)					October/2011 (low water)
Parameters	St. 1	St. 2	St. 3	St. 4	St. 5	St. 1	St. 2	St. 3	St. 4	St. 5
Cond.	8	9	5	18	10	11	9	6	21	13
pH	5.73	5.65	5.6	6.38	6.23	5.32	5.82	5.7	6.13	6.09
Turbid.	7.8	6.9	6.5	18	7.3	11	25	7	13	9
Silica	17	13	8	23	11	25	32	13	21	17
Alkal.	4.1	2.5	4.4	4	6	4.78	5.2	4.18	5.18	6.76
DO	5.4	5	5	4.6	4.8	5.2	4.8	5	5.2	5.7
BOD	13	10	11	21	8	11	21	9	14	6
Temp.	18	17	22	21	19	20	19	25	20	19
Phosp.	0.009	0.013	0.008	0.16	0.005	0.008	0.013	0.005	0.006	0.002
AmmNitrog	0.31	0.25	0.32	0.51	0.19	0.2	0.45	0.15	0.4	0.13
OrgNitrog	0.1	0.07	0.2	0.13	0.09	0.06	0.3	0.07	0.19	0.05
Depth	1.2	1.0	1.1	1.5	1.0	1.05	0.8	0.7	0.8	1.0

[1] *e-mail: biologavsm@gmail.com

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Investigação de depósito de espículas de esponjas de água doce em um lago cárstico no Brasil

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