Relationship between Bacteria, Nutrients and Rainfall in Selected Bodies of Fresh Water by DAVIDD. WOODBRIDGEand WILLIAMR. GARRETT University Center for Pollution Research Florida lnstitute of Technology Melbourne, Florida

The problem of the pollution of small man-made becoming

increasingly

boating,

or fishing signs posted around them.

lakes is

more evident by the number of no swimming,

vary in size usually ranging

These lakes

from 2 to 5 acres.

lakes are created by excavating of land for housing projects,

Many small

fill dirt during the development

highways,

recreational parks and

other projects. The excavations are then landscaped,

are allowed to fill with water,

the banks

and the lake is stocked with different

varieties

of fish.

The lake is then ready t o b e

used for

swimming,

boating,

fishing and other recreationsl

activities.

The small lakes also serve as a catchment basin for runoff water

from the surrounding

land area.

Many of these lakes

are Iocated in surburban areas without any sewage systems, thus relying on septic tanks as a means of sewage disposal. During heavy rainfall,

bacteria

laden effluent

tanks is washed into the lakes, nutrients

along with large quantities

in the form of fertilizer

the lakes there is no provision lake by streams or canals,

from the septic

from lawns.

for drainage

therefore,

accumulation point for bacteriological 311 Bulletin of En~ronmen~l Contammation & ~xieology, ~ 1 . ~ No. 5, 1 ~ ~ publi~ed ~ S~inge~VeHag New York Inc.

In many of

away from the

the lakes act as an pollutants,

chemical

of

pollutants,

and nutrient material.

The St. Johns river,

a natural drainage

for a large water

shed, was selected as a control

for this study.

up stream from the sample site,

is in a wild state, boardered

on either side by large marsh areas.

There are no inhabited

areas along this stretch of the river. down stream from the sampling Washington, water.

Approximately

5 miles

site the river flows into lake

from which several municipalities

The St. Johns River,

The river,

drew their raw

for this study, was designated

as sampling site #I. The selection

of two small lakes for this study was ba,

sed upon the conditions A small

existing

in the adjacent

lake located in a wooded area,

from the nearest dwelling, sample site #II.

about 88 mile distant

was selected and designated

The second

by a housing development

land areas.

as

lake is encompassed on two sides

and by business

establishments

on the

other two.

There are canals that flow through the.housing

development

into the lake.

This

lake was designated

as

sample site #III. Data A c q u i s i t i o n

and Methods

of Ana l~zin~

Samples were taken ai each site one day per week at approximately 24 weeks, chemical

the same time each sample day for a period of

resulting samples

in 24 b a c t e r i o l o g i c a l

for each sample site.

and 24

The water temperature

was taken at the time of each sampling. rainfall

samples

An average of the

for the six day period preceeding

each sample day

was calcul~ted. AIl sampling and methods

of analyses 312

of samples were

performed using standard me%hods DR-colorimeter

for the Hach model

and reagents by Hach Chemical Co. Ames Iowa.

The analyses performed I.

as adapted

and the methods

Dissolved Oxy@en - The method oxygen is a titrametric

used are as listed.

for analysis of dissolved

procedure

employing

the standard

W~inkler m~thod with the Alsterberg modification. sterberg m o d i f i c a t i o n larsene exide

substitutes

for the titration

W~inkler method,

The AI-

the stable reagent pheny-

of iodine in the standard

in place of unstable Sodium thiosulfate

reagent. 2.

N i t r a t e nitro~en - The m e t h o d nitrogen

is a colorimetric

for analysis

procedure

of nitrate

using the cadmium

reduction m e t h o d w~th l-napthylamine-sulfanific 3.

Ortho Phosphate

- The analysis

metric procedure

for phosphate

acid.

is a colori-

using thš molydate mehtod with stannous

reduction. 4.

Bacteriolo~ical

analysis

using the m i l l i p o r e

- These analyses were performed

filters

technique.

is placed in a sterile millipore bacteria

A sterile membrane

filter helder and the

are collected by passing the water sample through

membrane with the aid of a partial vacuum.

The membrane

and the side of the funnel are rinsed with a small volume of sterile distilled water.

The membrane

is removed asep-

tically and placed on an ~ b s o r b e n t disk previously with culture m e d i u m and contained The incubation

in sterile petri dish.

time and temperature

are specified

o r g a n i s m to be grown and m e d i u m used. M F - e n d o broth. dark

On this medium,

(purplishgreen)

saturated

for the

The m e d i u m used was

cell organisms

colonies with a metallic 318

that produce

sheen in 20• 2 hours at 35~

are classified as members of

the coliform group. Results Fi@ure 1 shows the variation of temperature of each of the three bodies of water, as a function of time.

from which samples were obtained,

The normal seasonal trend of the

water temperature is very evident from figure 1 with a minimum temperature in January of about 14~

and a maximum near 30~

in June. Figure 2 shows the six days accumulation of rainfall prior to the day to taking sample. are of significance.

Two periods of rainfall

These periods are the last half of

February and from the middle of April through the first part of June.

Between the period of considerable rainfall were

periods of dryness.

Both chemical and bacteriological poll-

ution conditions can be corralated with the periods of extensive rain. Figure 3 shows the occurance of phosphate in each of the bodies of water as a function of time.

There appears a fairly

excellant correlation of phosphate with rainfall except for one peak in the latter part of January.

The six days of rain-

fall before the February 20 data acquisition resulted in a small increase in phosphate at all three stations and the continued rain throughout the latter period of February and the first of March provided varying amounts of phosphate being washed into the St. Johns river,

314

and the lakes.

During the

summer of 1968, with the onset fairly heavy, middle of April a m a r k e d increase

rains in the

in phosphate

in the St. Johns River and in lake #II.

occured both

Both of these

bodies

of water received run-off water from an u n i n h a b i t e d

area.

Lake #III near a large number of homes and businesses

did not show the increase

in phosphate

until several weeks

after the onset of the summer rains. Fi@ure the bodies

4 showing n i t r a t e - n i t r o g e n

of w a t e r during the first half of 1968.

correlation

of the n i t r a t e - n i t r o g e n

very difficult

to relate directly

peak of rainfall

just before

shows a smmll increase water.

content of each of

The large increase

content of the water is

to rainfall.

the February

in nitrogen

Occurance

of n i t r a t e - n i t r o g e n

However,

the

20 date acquistion

in each of the bodies of

in n i t r a t e - n i t r o g e n

on the 9th of April cannot be accounted in rainfall.

Direct

that occured

for by an increase

of the relatively

high peak amount

in lake #II is indicative

of the condi-

tions that existed in the area before the lake was formed. Fi@ure

5 shows the total coliform as measured

per hundred mililiters water in which

in bacteria

of water in each of the 3 bodies of

samples were acquired.

A surprising

correla-

tion appears between the total coliform count and the nitratenitrogen,

in lake #III except for a few isolated points.

In

general,

the correlation between total coliform and nitrate-

nitrogen

is much greater than the generally

ship between total rainfall

accepted relation-

and eoliform in bodies of water.

315

The peaks in coliform, increases

in the St. Johns River, also follow

in the p h o s p h a t e in the river.

However,

the total

c o l i f o r m ~ount in the r e m o t e lake #II does hot c o r r e l a t e w i t h the o c c u r a n c e of either p h o s p h a t e or nitrate in the lake. However,

the increase in c o l i f o r m that occured at all stations

in A p r i l follow the i n c r e a s e in both p h o s p h a t e and n i t r a t e in these water. Discussion Results of the study indicates that the r e l a t i o n s h i p between dissolved nutrients and the i n d i c a t o r b a c t e r i a or direct.

such as p h o s p h a t e and n i t r a t e (total coliform)

are not simple

Under p a r ~ i c u l a r conditions in specific bodies

of w a t e r a d i r e c t r e l a t i o n s h i p may be shown.

However,

v a r i a b i l i t y in the d a t a w i t h time and in d i f f e r • of w a t e r raises doubts

the

bodies

as to the d i r e c t r e l a t i o n s h i p b e t w e e n

chemical and b a c t e r i a l pollutants. Sharpe increases in total c o l i f o r m occured i n both of the lakes that w e r e not r e l a t e d to r a i n f a l l in the area. In the St. Johns River the total c o l i f o r m c o r r e l a t e m u c h closer to the rainfall. increases

Even in the r~ver several sharpe

in total c o l i f o r m count o c c u r e d that w e r e not

o b v i o u s l y related to an increase in rainfall.

315

FIGURE

2

201 1.9 1.8 1.7 1.6 1.5 1.4 1.3

~1.2 ~1.1. 1.0

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1 24

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