LISTSERV mailing list manager LISTSERV 16.0

Help for WATERINSTITUTE-STU-L Archives


WATERINSTITUTE-STU-L Archives

WATERINSTITUTE-STU-L Archives


WATERINSTITUTE-STU-L@LISTS.UFL.EDU


View:

Message:

[

First

|

Previous

|

Next

|

Last

]

By Topic:

[

First

|

Previous

|

Next

|

Last

]

By Author:

[

First

|

Previous

|

Next

|

Last

]

Font:

Proportional Font

LISTSERV Archives

LISTSERV Archives

WATERINSTITUTE-STU-L Home

WATERINSTITUTE-STU-L Home

WATERINSTITUTE-STU-L  March 2008

WATERINSTITUTE-STU-L March 2008

Subject:

Seminar: Dissolved humic substances essential for freshwater life

From:

"Mckee,Kathleen A" <[log in to unmask]>

Reply-To:

Mckee,Kathleen A

Date:

Mon, 24 Mar 2008 13:28:24 -0400

Content-Type:

multipart/mixed

Parts/Attachments:

Parts/Attachments

text/plain (92 lines) , Steinberg-Gainesville.pdf (92 lines)

Seminar WEDNESDAY at UF - hosted by Soil and Water Science Department

Speaker:    Dr. Christian Steinberg, Institute of Biology, Humboldt Universitat zu Berlin
Location: McCarty A G186
Date:  3/26/2008
Time: 3-4pm

Title: Mild stress by dissolved humic substances is essential for freshwater life

Abstract  (also attached)

Despite their ubiquitous abundance in all freshwaters, the role of humic substances HS is

still inadequately understood. These substances have been considered too large to be taken

up by freshwater organisms. On the contrary, we present evidence that dissolved HS are

indeed taken up and interact with freshwater organisms. We show that dissolved HS exert a

mild chemical stress upon aquatic organisms in many ways; they induce molecular chaperones

(stress shock proteins: HSP70 as well as crystalline ones, which are known to play a

key role in lifespan extension), induce and modulate biotransformation enzymes. Furthermore,

they produce an oxidative stress. HS modulate the multixenobiotic resistance activity

and probably other membrane-bound exporters. This property may lead to an increased

bioaccumulation of xenobiotic chemicals. The talk will focus on three topics.

Feminizing potential: HS can modulate the numbers of offspring in a nematode and feminize

fish (Fig. 1) and amphibians. In a recent study, we asked whether this potential applies

to humic substances in general. With quantitative PCR of the genes of the nematode

Caenorhabditis elegans, we showed that all humic substances studied induced the vitellogenin

gene induction, (vitellogenin is the most prominent yolk protein), hence, this finding

indicates a general feminizing property of humic substances even to invertebrates. The estrogenic

pathway is one of the potential modes of action.

Fish life in acidic freshwaters: In very soft, humic freshwaters, such as the Amazonian Rio

Negro, Brazil, HS stimulate the uptake of essential ions, such as Na and Ca, at extremely

low pH (3.5-4.0) and prevent the ionoregulatory disturbance induced by acid waters,

thereby enabling fish to survive in these environments. We re-visit recent papers on fish adaptation

in the Rio Negro and re-interpret the results on the basis of the recent finding of

gene control in the nematode Caenorhabditis elegans. In the nematode, several genes are

up-regulated. This may also account for the maintenance of fish life in the Rio Negro.

Lifespan extension: Exposure to HSs exerts mild chemical stress on the exposed organisms

and deprives them of energy; however, the compost dweller C. elegans actively looks

for such environments. With life-table and DNA gene filter studies we show that HSs may

cause longevity and multiple stress resistance. With C. elegans, a lifespan extension was

induced with certain HS qualities. Intrigued by this result, we studied the potential of lifespan

extension with other animals, for instance the water flea, Daphnia magna. Upon exposure to

HS, the usually parthenogenetic females (reproduction without males) started to produce

males. Subsequently, males and females were separately exposed to HS. Surprisingly, the

lifespans of males was extended, but not that of females, rather their lifespan was reduced.

We do not yet understand the ecological consequences, and possible advantages and disadvantages

of this.

In sum, dissolved HS interact with freshwater organisms in a variety of ways in unenriched

humic lakes. In addition to the well known effects of HS on light regime, for example, and

the direct and indirect supply with carbon (energy), other interactions may be much more

subtle. We are just at the beginning of understanding that these interactions between dissolved

HS and freshwater organisms indicate HS features as an ecological driving force.

Top of Message | Previous Page | Permalink

Advanced Options


Options

Log In

Log In

Get Password

Get Password


Search Archives

Search Archives


Subscribe or Unsubscribe

Subscribe or Unsubscribe


Archives

January 2021
December 2020
November 2020
October 2020
September 2020
August 2020
July 2020
June 2020
May 2020
April 2020
March 2020
February 2020
January 2020
December 2019
November 2019
October 2019
September 2019
August 2019
July 2019
June 2019
May 2019
April 2019
March 2019
February 2019
January 2019
December 2018
November 2018
October 2018
September 2018
August 2018
July 2018
June 2018
May 2018
April 2018
March 2018
February 2018
January 2018
December 2017
November 2017
October 2017
September 2017
August 2017
July 2017
June 2017
May 2017
April 2017
March 2017
February 2017
January 2017
December 2016
November 2016
October 2016
September 2016
August 2016
July 2016
June 2016
May 2016
April 2016
March 2016
February 2016
January 2016
December 2015
November 2015
October 2015
September 2015
August 2015
July 2015
June 2015
May 2015
April 2015
March 2015
February 2015
January 2015
December 2014
November 2014
October 2014
September 2014
August 2014
July 2014
June 2014
May 2014
April 2014
March 2014
February 2014
January 2014
December 2013
November 2013
October 2013
September 2013
August 2013
July 2013
June 2013
May 2013
April 2013
March 2013
February 2013
January 2013
December 2012
November 2012
October 2012
September 2012
August 2012
July 2012
June 2012
May 2012
April 2012
March 2012
February 2012
January 2012
December 2011
November 2011
October 2011
September 2011
August 2011
July 2011
June 2011
April 2011
March 2011
February 2011
January 2011
December 2010
November 2010
October 2010
September 2010
August 2010
July 2010
June 2010
May 2010
April 2010
March 2010
February 2010
January 2010
December 2009
November 2009
October 2009
September 2009
August 2009
July 2009
June 2009
May 2009
April 2009
March 2009
February 2009
January 2009
December 2008
November 2008
October 2008
September 2008
August 2008
July 2008
June 2008
May 2008
April 2008
March 2008
February 2008
January 2008
December 2007
November 2007
October 2007
September 2007
August 2007

ATOM RSS1 RSS2



LISTS.UFL.EDU

CataList Email List Search Powered by the LISTSERV Email List Manager