University of South FloridaScholar Commons

Reports Tampa Bay Area Study Group Project

1-1-2002

Historical and current observations on macroalgaein the Hillsborough Bay EstuaryJ.O.R. JohanssonBay Study Group, City of Tampa

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Scholar Commons CitationJohansson, J.O.R., "Historical and current observations on macroalgae in the Hillsborough Bay Estuary" (2002). Reports. Paper 38.http://scholarcommons.usf.edu/basgp_report/38

HISTORICAL AND CURRENT OBSERVATIONS ON MACROALGAE IN THE HILLSBOROUGH BAY ESTUARY (TAMPA BAY), FLORIDA. Johansson, J.O.R., Bay Study Group, City of Tampa, Tampa FL. Complaints from citizens of Tampa in the early 1960's about obnoxious odors emanating from decaying macroalgae (Gracilaria) along the western shore of Hillsborough Bay resulted in one of the earliest studies undertaken to control eutrophication of an estuary. Results from the study, which were published in 1969, linked the build-up of macroalgae along the shore, and poor bay water quality, to wastewater discharges to the bay with high nutrient and organic content. The study identified the City of Tampa’s wastewater plant and the Central Florida fertilizer industry as the two major sources of nutrient pollution to the bay. The study concluded that large reductions of nutrient discharges were needed from these sources, specifically of nitrogen, to improve water quality and to restore a diverse ecosystem to the bay. From the mid 1970's to the early 1980's, local and state regulations, primarily aimed at reducing point-source nutrient pollution, resulted in large phosphate reductions and a near 65% reduction in dissolved inorganic nitrogen discharges to the bay. By the mid 1980's, Hillsborough Bay showed signs of lessened eutrophication. These signs included a near 50 percent decrease in phytoplankton biomass and new growth of submerged seagrass. Despite the nutrient reductions, macroalgae biomass appeared to remain high and odor complaints were still being received by the City of Tampa from citizens on the western side if Hillsborough Bay. In 1983, the city contracted for a year-long study of macroalgae biomass and distribution in the bay. Surprisingly, this study found areas with much higher biomass than that reported in the 1969 study. Attempts to link macroalgae biomass to bay water quality and other potentially important variables were inconclusive in this study. To improve the understanding of macroalgae dynamics it was recommended that long-term monitoring of the macroalgae in the bay be initiated. Subsequently, the City of Tampa initiated a Hillsborough Bay macroalgae monitoring program that since 1986 has been providing consistent monthly biomass and species composition information from five fixed transects. In addition to the transect monitoring, low level aerial observations are conducted on a near monthly schedule for estimations of bay-wide macroalgae and seagrass coverage. Results indicate that the annual bay-wide macroalgae coverage has decreased near steadily from about 300ha in the late 1980's to less than 30ha since 1997. Estimated average monthly bay biomass has decreased from a peak of near 150tons wet weight in 1988 to less than 1ton wet weight since 1997. Macroalgae species composition during the 15 year monitoring period has often been dominated both in terms of biomass and frequency of occurrence by Gracilaria spp. Other major species include: Spyridia filamentosa, Ulva lactuca, Agaridhiella tenera, and the attached alga Caulerpa prolifera

HISTORICAL AND CURRENT HISTORICAL AND CURRENT OBSERVATIONS OF MACROALGAE IN OBSERVATIONS OF MACROALGAE IN HILLSBOROUGH BAY (TAMPA BAY), HILLSBOROUGH BAY (TAMPA BAY),

FLORIDAFLORIDA

CITY OF TAMPACITY OF TAMPABAY STUDY GROUPBAY STUDY GROUP

J.O.R. JOHANSSONJ.O.R. JOHANSSONW. M. AVERYW. M. AVERYG.V. PINSONG.V. PINSON

K.B. HENNENFENTK.B. HENNENFENTJ.J. PACOWTAJ.J. PACOWTA

TAMPA BAY AND WATERSHEDTAMPA BAY AND WATERSHED

HILLSBOROUGH BAYHILLSBOROUGH BAY

HISTORICALHISTORICAL BACKGROUNDBACKGROUND

BAYSHORE BLVD.BAYSHORE BLVD.

2635

91

1029 FERTILIZERIND+ALAFIA RCITY OF TAMPA

OTHERS

8670

130

450

DINDIN TPTP

DIN AND TP LOADING TO HILLSBOROUGH BAY IN 1967DIN AND TP LOADING TO HILLSBOROUGH BAY IN 1967--6868

mtonsmtons/yr/yr

TAMPA TRIBUNE NOVEMBER 16, 1969TAMPA TRIBUNE NOVEMBER 16, 1969

0

5

10

15

20

25

30

35

40

45

50

1956 1961 1966 1971 1976 1981 1986 1991 1996 2001

YEAR

PO4,

ppm

ALAFIA RIVER PO4 CONCENTRATIONSALAFIA RIVER PO4 CONCENTRATIONS

DIN LOAD FROM COT WWTP AND NITRAM INC.

0

500

1000

1500

2000

2500

3000

3500

4000

4500

1952 1955 1958 1961 1964 1967 1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000

YEAR

DIN

LO

AD

, mto

ns/y

r

COT WWTP NITRAM INC.

DIN LOAD AND CHLOROPHYLLHILLSBOROUGH BAY

0

500

1000

1500

2000

2500

3000

3500

4000

4500

1968 1971 1974 1977 1980 1983 1986 1989 1992 1995 1998

YEAR

DIN

LO

AD, m

tons

/yr

0

10

20

30

40

50

60

CH

LOR

OP

HY

LL-a

, ug/

l

DINLOAD CHLOROPHYLL

AUGUST 1991AUGUST 1991

OCTOBER 2001OCTOBER 2001

JANUARY 1984JANUARY 1984

CITY OF TAMPA MACROALGAE CITY OF TAMPA MACROALGAE MONITORINGMONITORING

TRANSECT SAMPLINGTRANSECT SAMPLING

MONITORING TRANSECTSMONITORING TRANSECTS

CITY OF TAMPA MACROALGAE CITY OF TAMPA MACROALGAE MONITORINGMONITORING

AREALAREAL COVERAGECOVERAGE

FLIGHT PATHS AND MACROALGAE AERIAL OBSERVATIONSFLIGHT PATHS AND MACROALGAE AERIAL OBSERVATIONS

MONTHLY AREAL COVERAGE AND TRAWL ESTIMATED BIOMASS OF MACROALGAE IN HILLSBOROUGH BAY

0

100

200

300

400

500

600

700

1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

YEAR

CO

VER

AG

E, h

a

0

50

100

150

200

250

300

350

TRA

NSEC

T BI

OM

ASS

, gw

w/m

2

COVERAGE

TRANSECTBIOMASS

MACROALGAE AREAL COVERAGE AND BIOMASS IN HILLSBOROUGH BAY

0

50

100

150

200

250

300

350

400

1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

YEAR

ANN

UAL

AV

ERA

GE

CO

VER

AG

E, h

a

0

50

100

150

200

ANN

UALA

VER

AG

E BI

OM

ASS

, mto

nsw

w

COVERAGE

BIOMASS

MACROALGAE MACROALGAE COMPOSITIONCOMPOSITION

GRACILARIA VERRUCOSAGRACILARIA VERRUCOSA

GRACILARIA SP. 2GRACILARIA SP. 2

SPYRIDIA FILAMENTOSASPYRIDIA FILAMENTOSA

ULVA LACTUCAULVA LACTUCA

AGARDHIELLA TENERAAGARDHIELLA TENERA

CAULERPA PROLIFERACAULERPA PROLIFERA

MACROALGAE SPECIES OCCURRENCE AND BIOMASS (TRAWL COLLECTIONS)

0

1000

2000

3000

4000

5000

6000

7000

Grac. ve

rr.Spy

r. fil.

Ulva la

tac.

Agar. t

enera

Grac. S

p.2

Chaeto

m. grac

.

Chaeto

m. cras

saCau

l. prol

if. 18 14 11 27 6 23 12 15 8 22 24 26 25 16

SPECIES

TOTA

L B

IOM

ASS,

gw

w/m

2

0

100

200

300

400

500

600

700

CO

UN

T O

F O

CC

UR

REN

CE

BIOMASS

OCCURRENCE

ANNUAL MACROALGAE SPECIES COMPOSITION (TRAWL COLLECTIONS)

0

10

20

30

40

50

60

70

80

1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

YEAR

BIO

MAS

S, g

ww

/m2

Grac. verGrac. sp. 2Agar. teneraUlva lact.Spyr. fil.

MACROALGAE COMPOSITION BY MONTH (TRAWL COLLECTIONS)

0

5

10

15

20

25

30

1 2 3 4 5 6 7 8 9 10 11 12

MONTH

BIO

MAS

S, g

ww

/m2

Grac. verrGrac. sp. 2Agar. teneraUlva lact.Spyr. fil.

CONCLUSIONCONCLUSION

MACROALGAE AND SEAGRASS COVERAGE, AND CHLOROPHYLL-a CONCENTRATIONS IN HILLSBOROUGH BAY

0

50

100

150

200

250

300

350

40019

50

1952

1954

1956

1958

1960

1962

1964

1966

1968

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

YEAR

MAC

ROA

LGAE

AND

SEA

GRA

SS C

OVE

RAG

E,

ha

0

10

20

30

40

50

60

70

80

CHL

OR

OPH

YLL-

a CO

NCE

NTR

ATI

ON

, ug/

l

MACROALGAE COVERAGE

SEAGRASS COVERAGE

CHLOROPHYLL-a CONC

Valiela, et al. 1997

THE ENDTHE END